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Bio 12: Unit 9
The Nervous System
| Question | Answer |
|---|---|
| What does survival depend on (in part)? | the ability to respond to changes that occur within the body and the environment around it. |
| What is the nervous system? | our processing system that keeps us in contact with the outside world |
| What are the roles of the nervous system responsible for? | coordination of movement, response to environmental stimuli, intelligence, self-awareness, thought, emotion |
| What is the nervous system composed of? | composed of nerve cells called neurons which are specialized to carry nerve impulses. |
| What are the two major divisions of the nervous system? | The central nervous system and the peripheral nervous system. |
| What does the central nervous system include? | includes the spinal cord and the brain. It is in the centre of the body. |
| What does the peripheral nervous system include? | The rest of the nervous system. It further divides into the Somatic (connects to skeletal muscles) and automatic (connects to smooth muscles) nervous systems. |
| What does the Autonomic nervous system further divide into? | the Sympathetic (emergency situations) and Parasympathetic (normal state, usually depresses) nervous systems |
| What are nerve cells called? | neurons |
| What are the three parts of a neuron? | 1) Dendrite, 2) Cell body, 3) Axon |
| What does a dendrite do? | dendrites conduct nerve impulses towards the cell body |
| What does an axon do? | axons conduct nerve impulses away from the cell body. |
| What are dendrites and axons sometimes called? | fibers |
| What usually covers long fibers (like the axon)? | a myelin sheath that is secreted by schwann cells (eacho of which has a nucleus) |
| What are the spaces between myelin sheaths called? | nodes of ranvier |
| What are the 3 types of NEURONS? | Sensory Neuron, Motor Neuron, Interneuron |
| How are the spinal nerves connected to the CNS? What does it create? | connected to the CNS on either the dorsal or ventral side of the spinal cord creating roots. |
| What does a sensory neuron look like? | Sensory neurons have long dendrites. It has a relatively short axon and enters CNS from the cell body. |
| What does a motor neuron look like? | axon is the longest fibre in a motor neuron. |
| What does a sensory neuron do? | They have long dendrites that extend from receptors towards the CNS and pass through the dorsal root to the cell body. This allows it to take msgs from a sense organ to the CNS. |
| What does a motor neuron do? | Extends from motor neuron's cell body, located w/in CNS, throughout the ventral root and conducts impulses to an effector. This allows it to takes msgs away from CNS to muscle fibre or gland |
| What does an interneuron look like? Where are they located? | Located entirely within the CNS. It has a short axon. |
| What does an interneuron do? | it interconnects nerve cells. Conveys msgs btwn parts of the system. |
| What does the spinal cord look like? What are the components? | Cell bodies of motor neurons, coupled with interneurons, give inner regions of the spinal cord a darker colour. |
| What is the inner region of the spinal cord called? | gray matter |
| What is the outer region of the spinal cord called? | white matter |
| What is a nerve? | a combination of nerve fibres |
| What is a neuron? | a nerve cell |
| What are mixed nerves? | nerve tissue composed of bundles of long fibres of neurons |
| Is the white line that can be seen in a disected animal a nerve or a neuron? | it is a nerve |
| What can be seen in the same nerve? | dendrites of sensory neurons and axons of motor neurons. |
| How can you describe nerve conduction? | nerve conduction is an electrochemical change that moves in one direction along the length of a nerve fibre. |
| Why is it an electrochemical change? | it involves changes in voltage and concentrations of certain ions. The movement of ions creates a temporary shift in the electrical nature of the fibre. |
| What are the 3 phases of a nerve impulse along an axon? | Resting phase, Action phase, Recovery phase. |
| What is resting potential? | When NOT conducting impulses, voltage difference across the membrane of the axon of about -60mV. It is when the axoplasm (cytoplasm of the axon) has a slight negative charge. |
| Why is there a negative charge inside the axon during resting potential? What is the composition of the axon like? | There is a presence of large negative ions. There are more Na+ ions on the outside of the axon compared to the inside, and there are more K+ ions and negative ions on the inside compared to the outside. |
| At resting potential, is the membrane permeable? | No it is not. The axomembrane contains Na/K pumps that are responsible for establishing and maintaining an unequal ion distribution of resting potential. |
| What is Action Potential | when a nerve is stimulated by electric shock, pH change, mechanical stimulation, a nerve impulse is generated. |
| What happens when a nerve impulse is generated? | a stimulus that surpasses the threshold value disrupts the axomembrane and suddenly makes it premeable to Na+. |
| What is depolarization or the upswing? | It is when Na+ ions flood to the axoplasm through sodium gates. |
| What happens to the electrical difference during depolarization? | This reverses the electrical difference in the axomembrane. Axoplasm now has a net positive charge relative to the outside. Axoplasm is now at +40mV relative to the outside. |
| After the axoplasm is at +40mV what happens to the axoproteins? | Na+ gates close and K+ gates open |
| What is repolarization or the downswing? | It is when K+ ions flood to the outside of the axon. This restores the normal polarity of the ion. (back to -60mV) |
| What occurs after repolarization? | The Na/K pump returns the ions to their starting places and neurons return to rest (done actively, not passive) |
| What does the "all or none" impulse mean? | it means that as long as the threshold stimulus was reached, there will be an impulse. It will not be stronger than another impulse, all impulses are equal. |
| If all impulses are equal, what happens when there is a stronger stimulus? | There are a greater number of impulses. |
| In terms of impulses, why are vertebrates different? | nerve impulses jump from node to node (node of ranvier) in myelinated fibre. |
| In terms of impulses, why are non-myelinated fibres different? | nerve impulses must depolarize and repolarize each point along the nerve fibre. |
| How fast are transmissions in myelinated and non-myelinated fibres? | 200m/s vs. 0.5m/s |
| What is saltatory transmission? | the "jumping transmission" that occurs in myelinated fibres. |
| What is a synapse? | the region between the end of an axon and the cell body or dendrite to which it is attached |
| What are synaptic endings? | swollen terminal knobs on the ends of axon terminal branches |
| What is the presynaptic membrane? | the membrane of the axon synaptic ending |
| What is the postsynaptic membrane? | the membrane of the next neuron just beyond the axon's synaptic membrane. |
| What is the synaptic cleft? | the space between the presynaptic and the postsynaptic membranes |
| What are neurotransmitters? | chemicals that transmit the nerve impulses across a synaptic cleft. They are small molecules. Can be single amino acids, short chains of amino acids or derivatives of protein |
| What are synaptic vesicles? | the contain neurotransmitters and are contained near surface of synaptic endings |
| Name four important neurotransmitters | Acetylcholine (Ach), Noradrenalin (NA), Serotonin, Adrenalin |
| What does transmission across synapses only occur one way? | because only the ends of axons have synaptic vesicles that are able to release neurotransmitters to affect the potential of the next neurone. |
| What is the first step of transmission across a synapse? | the nerve impulse travels along the axon and reach the synaptic ending |
| What is the second step of transmission across a synapse? | Nerve impulses change the presynaptic membrane and CA++ flows into the synaptic ending. |
| What is the third step of transmission across a synapse? | Ca++ ions cause contractile proteins to pull synaptic vesicles to the inner surface of the presynaptic membrane |
| What is the fourth step of transmission across a synapse? | The synaptic vescle fuses with the presynaptic membrane and by exocytosis, releases neurotransmitters into the synapse. |
| What is the fifth step of transmission across a synapse? | Neurotransmitters diffuse across the synaptic cleft to receptors on postsynaptic membrane. Receptors control selective ion channels; binding of a neurotransmitters to its specific receptor opens the ion channels |
| What is the sixth step of transmission across a synapse? | Ion flux changes the voltage of the postsynaptic membrane. Either moves the membrane closer to the threshold voltage required for an action potential (excitory synapse) OR hyperpolarizes the membrane (inhibitory synapse) |
| What is the last step of transmission across a synapse? | Neurotransmitters are quickly deactivated to prevent them from continually acting on the post synaptic membrane. |
| How are neurotransmitters deactivated? | 1) degraded by an enzyme, 2) synptic ending reabsorbs the neurotransmitters (happens to serotonin) |
| What does proper brain and nervous system function depend on? | the proper balance of exitory and inhibitory synaptic transmitters |
| Name some excitatory transmitters | Acetylcholine, adrenalin, noradrenalin, serotonin, dopamine |
| What are some inhibitory transmitters? | GABA, glycine, sometimes serotonin |
| How much information might a single neuron receive? | may receive information from thousnads of neighbouring neurone through thousands of synapses. Some are excitory, others are inhibitory |
| What oes the Peripheral Nervous System consist of? Why? | nerves that contain ONLY long dendrites and/or long axons. Because neuron cell bodies are found only in the brain, spinal chord and ganglia |
| What are Ganglia? | collections of cell bodies within the PNS |
| What are the 3 types of NERVES. | Sensory nerves, Motor nerves, Mixed nerves |
| What do sensory nerves contain? | only long dendrites of sensory neurons. |
| What do motor nerves contain? | only long axons of motor neurons. |
| What do mixed nerves contain? | both the long dendrites of sensory neurons and the long axons of motor neurone |
| How many cranial nerves are attached to a human brain? What are cranial nerves part of? What does it consist of? | 12 pairs of cranial nerves. Part of the PNS. Some are sensory, motor and mixed. |
| What do the cranial nerves serve? | the head, neck and face regions (except the Vagus nerve which branches to serve internal organs) |
| How many pairs of spinal nerves are there in a human? | 31 pairs. |
| What are spinal nerves? | mixed nerves that leave the spinal chord by two short branches (called roots) which lie within the vertebral column. |
| What is a dorsal root? | one of the two roots of a spinal nerve that passes dorsally to the spinal cord and that consists of sensory fibers. |
| How can the dorsal root be identified? | identified by the presence of an enlargement called the dorsal root ganglion |
| What does the dorsal root ganglion contain? | the cell bodies of the sensory neurons whose dendrites conduct impulses towards the cord |
| What is a ventral root? | one of two the two roots of a spinal nerve that passes ventrally from the spinal cord and that consists of motor fibers. |
| What does the ventral root contain? | contains axons of motor neurons that conduct impulses away from the cord. |
| What does the SOMATIC nervous system include? | all the nerves that serve the musculoskeletal system and the exterior sense organs (including skin). |
| What are exterior sense organs (in terms of the stimulus)? | receptors that receive environmental stimuli and begin nerve impulses |
| What are muscle fibres (in terms of the stimulus)? | effectors that react to the stimulus |
| What are reflexes? | automatic, involuntary responses to changes occurring inside or outside the body (may or may not involve the brain). Reflexive actions are protective mechanisms. |
| What is the reflex arc? | the main functional unit of the nervous system, usually involves all three types of neurons. |
| What does the reflex arc allow us to do? | allows us to react o internal and external stimuli |
| What is the first step in the path of a simple reflex arc? | 1) receptor generates a nerve impulse (ex. pain receptor in the skin) |
| What do receptors do? (in terms of the reflex arc) | detects stimuli that surpasses the threshold and initiates impulses. |
| What is the second step in the path of a simple reflex arc? | Sensory neuron takes the msg to the CNS. impulse moves along the dendrite, proceed to cell body (in dorsal root ganglia) and then go from cell body to axon in gray matter of cord |
| What is the third step in the path of a simple reflex arc? | The interneuron passes the msg to the motor neuron. (Other interneurons will conduct impulses to the brain to alert the conscious mind that a reflexive action took place. |
| What is the fourth step in the path of a simple reflex arc? | Motor neuron takes msg away from the CNS to axon of the spinal nerve |
| What is the fifth step in the path of a simple reflex arc? | Effector receives nerve impulses and reacts (gland will secrete and muscles will contract) |
| What is the autonomic nervous system made of? | it is part of the PNS and is made of motor neurone that control the internal organs automatically and usually, unconsciously |
| What is the autonomic nervous system divided into? | the sympathetic and parasympathetic nervous systems - each connect to the same organs, but with different effects |
| How does the autonomic nervous system function? | it functions unconsciously on internal organs and utilizes two motor neurone and one ganglion for each nerve impulse. |
| What is the difference between the sympathetic and parasympathetic nervous systems? | Sympathetic promotes active body functions, parasympathetic controls the opposite. It is usually termed vegetative. |
| How does the antagonistic relationship between the sympathetic and parasympathetic systems affect the body. | In their activity, they help the body maintain homeostasis |
| When is the sympathetic nervous system important? | during emergency situations, it is associated with the "Fight or Flight" reaction |
| What does the sympathetic nervous system cause the body to do during emergencies? (7) | 1)energy directed away from the digestion, 2)pupils dilate (take in all info), 3)heart rate increases (incase muscles need to act), 4)perspiration increase, 5)salvation decrease, 6)breathing rates increase, 7)promote conversion of glycogen to glucose |
| What neurotransmitter is released by the postganglionic axon of the Sympathetic nervous system? | Nordarenalin - accelerates the heart rate. |
| Where do the fibres for the sympathetic nervous system come from? | Comes from the middle part of the spinal cord. AKA the thoracic-lumbar. |
| What does the parasympathetic nervous system promote? Examples (4) | promotes all the internal responses associated with a relaxed state. Causes the pupils to contract, energy is diverted for digestion of food, heart rate slows. |
| What neurotransmitter is associated with the parasympathetic nervous system? | Acetylcholine - causes a relaxed state |
| Where do the fibres for the parasympathetic nervous system come from? | comes from the upper and lower part of the spinal cord - AKA the cranial and sacral nerves. |
| Where does brain development start? | starts in embryos as series of enlargements at the anterior end of the neutral tube ->develops into spinal cord. Enlargements become cerebrum and cerebellum, and other structures that are adjacent to the cerebrum and cerebellum. |
| How many pairs of nerves extend out from the brain to the body region? What are they called? What do they do? What are they part of (what system)>\? | 12 pairs of nerves, cranial nerves, allows responses to various stimuli, part of the peripheral nervous system |
| What is the cerebrum? | it is the largest portion of the brain and is divided into the right and left hemisphere by the central fissure |
| What is at the base of the central fissure? | a dense tissue called the corpus callosum |
| If one cuts down the central fissure, through the corpus callosum, and down into the spinal cord, what view would you have of the brain? | Sagittal |
| What does the cerebrum do? | it is the central processing area of the brain. It is where memory is kept, where conscious thoughts are made and where a lot of non-reflectxive connections and associations are made. |
| What does the cerebrum look like? | it is a large, complex region that has its own subdivisions called lobes and areas of specializations within the subdivisions. |
| What kind of impulses are sent to the cerebrum? | impulses that require processing before responding are sent to this part of the brain. |
| Where is the medulla oblongata located? | it lies closest to the spinal cord |
| What does the medulla oblongata control? | heart rate, breathing rate, blood pressure, reflex reactions like coughing, sneezing, vomiting, hiccoughing, swallowing |
| What do pons do? | Pons have ganglia that regulate the breathing centres in the medulla |
| What does the Thalamus do? | it receives sensory information from all parts of the body and channels hem to the cerebrum. |
| What does the Thalamus serve as? | it serves as a central relay station for sensory impulses, it is the last portion of the brain for sensory input before the cerebrum. It receives all sensory impulses except for smell and sends them to appropriate regions of the cortex. |
| What is the thalamus a part of? What does that do? | It is part of the reticular activating system (RAS) it sorts out incoming stimuli, passing on to the cerebrum only those that require immediate attention. The RAS extends from the medulla oblongata to the thalamus |
| What does the cerebellum do? | it controls balance and complex muscular movement. |
| In the cerebellum, what are impulses used for? | used to ensure that motor impulses provide smooth movements and the body can maintain its sense of balance and coordination. |
| What is the cerebellum responsible for? What does it fnction in?u | it is responsible from maintaining normal muscle tone, posture and balance. functions in muscle coordination and makes sure seletal muscles work together smoothly. |
| Where does the cerebellum receive information? | it receives sensory information from the inner ear |
| Why is the hypothalamus important? | it maintains the internal environment. It is the centre for homeostasis |
| How does the hypothalamus work? | it detects adjustments then initiates nerve responses or release hormones. |
| Where is the hypothalamus located? | below the thalamus |
| What does the hypothalamus contain centres for? What does it control? | hunger, sleep, thirst, body temperature, water balance, blood pressure. It controls the pituitary gland |
| What is the corpus collasum? What does it do? | it is a horizontal connecting piece btwn the two hemispheres of the brain. It transmits information btwn the right and the left hemispheres. |
| If the corpus collasum separates the brain, what does the mean for the brain and it's processing system? | it means the the two sides of the brain function separately. |
| Reactions of the medulla oblongata vs. the hypothalamus | medulla=rapid, hypothalamus=much slower. |
| What does the CNS consist of? | The brain and spinal cord |
| What is received by the CNS and what is initiated by it? How is it protected? | receives sensory information, initiates motor control. protected by bones and are wrapped up in protective membranes called meninges. |
| Where is the spinal cord found? Where does it extend? | it extends from the brain down the back through the vertebrae. |
| What are the 4 regions of the spinal cord? | cervical, thoracic, lumbar and sacral |
| What does the cervical region deal with? | corresponds to the neck |
| What does the thoracic region deal with? | corresponds to the thoracic cavity |
| What does the lumbar region deal with? | corresponds to the lower back |
| What does the sacral region deal with? | corresponds to the tailbone area. |
| What branches out of the spinal cord? | peripheral nerves branch out into the body from between most vertebrae. It usually originates from the lower of the three regions |
| What is the brain surrounded by to protect it? | cranium |
| What is the spinal cord surrounded by to protect it? | the vertebrae |
| What are the 3 types of meninges? | 1) closest to bone=dura mater, tough layer, 2)middle layer=vascularized arachnoid layer, 3) next to nerve tissue = pia mater |
| What does the right hemisphere control? | The left side of the body (except smell), intuitive/creative side. |
| What does the left hemisphere control? | The right side of the body, logical side |
| What are the two lobes of the pituitary gland? Where do they extend from? | The anterior and posterior, both extend from the hypothalamus |
| What is neuroendocrine control? | when blood passes through the hypothalamus and its composition and temperature stimulates various homeostatic responses |
| What does the anterior lobe release? ex. | it releases a set of hormones that have a range of effects. Ex. brings changes associated with reproduction and skeletal growth |
| What does the posterior lobe release? ex. | releases ADH (plays role in the urinary system) and oxycotin (a hormone of the reproductive system) |
| What is the mechanism of action for anterior pituitary hormones? | hypothalamus detects that effect of hormone from A.P. is required, it release a "releasing hormone" that travels through a short portal system that interconnects with the A.P. Release hormones trigger secretion of the required hormone from the A.P. |
| What is a portal system | a set of blood vessels that have a capillary bed on each side. |
| What is the mechanism of action for posterior pituitary hormones? | hypothalamus produce hormones that are stored and release by the P.P. Nerve tracks (extend from hypothalamus) control their release. |
| What is gray matter and what does it contain? | it is the inner layer of the spinal cord. Contains cell bodies of neurons and short fibres. |
| What is white matter and what does it contain? | it is the outer layer of the spinal cord and contains long fibres of interneurons |
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