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CNS
Physiology
| Question | Answer |
|---|---|
| What do you taste when you eat something sweet? | Metabolic energy |
| What do you taste when you eat something sour? | Acidic pH |
| What do you taste when you eat something bitter? | Poisons |
| What do you taste when you eat something salty? | Ion concentration (Na) |
| What do you taste when you eat something oriental (umami)? | Amino acids |
| Explain the pathway from tastant --> actually tasting it (ie part of the brain nerves go to) | Buds in papilla --> afferent neuron --> cranial nerves 7 and 9 --> (pons) --> thalamus -->sensory cortex |
| Explain what happens when you eat something salty or sour | Na, K, H --> change in ion concentration --> response |
| Explain what happens when you eat something sweet, bitter or umami | Tastant --> reaction with specific receptor molecules on cell surface --> G-protein --> response |
| How come dogs have a better sense of smell than us? | Larger olfactory epithelium, larger olfactory bulb and more functional olfactory receptors |
| How many receptor cells to one mitral cell? | 1000 = increased sensitivity but decreased localisation |
| Is there lateral inhibition anywhere? | Yes, between the two sides of the nose (slight localisation) |
| Describe the olfactory pathway | Olfactory tracts --> sensory cortex and limbic system (motivation) --> hypothalamus and reticular formation (arousal) --> pituitary (reproduction) OLD LADIES HAVE PROBLEMS REPRODUCING!!!! |
| What must odorant molecules be? | Lipid soluble |
| What happens when your exteroreceptors sense a really hot temperature? | The cold receptors fire |
| Do the neurones in the same strip of skin go to the same dorsal root ganglion? | Yes :) |
| What two types of nerve endings do you have? | Naked nerve endings (hairy skin) and encapsulated nerve endings (hairless skin - eyelids, palms, lips) |
| What do naked nerve endings sense? | Cold and pain |
| What do encapsulated nerve endings sense? | Pressure |
| What are the different types of encapsulated nerve endings? | Pacinian corpuscles (localised), Ruffini endings (tension), Merkeli disc (deformation), Meissners corpuscles (shearing) |
| What afferent signals do type I fibres transmit? | Proprioception |
| What afferent signals do type II fibres transmit? | Touch and kinesthesia |
| What afferent signals do type III fibres transmit? | Touch, temperature and (fast) pain |
| What afferent signals do type IV fibres transmit? | Touch and (slow) pain |
| What pathways go through the dorsal columns and ventro-lateral system? | Touch and pain respectively |
| What substances are released when tissue is damaged? What fibres do they activate? | Bradykinin and Substance P Type IV fibres |
| Describe the gate control theory of pain | It alleviates pain by stimulating larger sensory fibres in the skin e.g. temperature and pressure |
| What is the other pain pathway? (other than the gate control theory) Describe it | Descending pathway Pain through type IV fibres --> spinal cord --> thalamus via ventro-lateral system --> periaqueductal gray --> raphe nucleus --> inhibition of type IV fibres!!! |
| What stimulates the descending pathway? | Morphine |
| What senses proprioception? What type of movement does each detect? | Vestibular apparatus Semicircular canals - rotational movement, otolith organs - linear acceleration |
| What is the pathway of proprioception (how does the info get from the vestibular apparatus to the brain)? | Vestibular apparatus --> CN 8 --> vestibular nucleus --> cerebellum |
| What happens in the otolith organs when the head is tilted or accelerated forward (or backward :P)? | The stereocilia bend toward the kinocilium (excited), they bend away from the kinocilium if inhibited |
| What direction are the cells of the otolith organs orientated in? | All different directions |
| What happens when the cells of the semicircular canals are excited? | When the head is rotated to the right, the stereocilia on the cells on the left bend away from the kinocilium and are therefore inhibited, the stereocilia on the cells on the right bend toward the kinocilium and are therefore stimulated |
| What do muscle spindles give information about? | Stretch and length |
| What type of fibres are in a muscle fibre? | Extrafusal |
| What type of fibres are in a muscle spindle? | Intrafusal |
| What type of fibres supply a muscle fibre? | Alpha |
| What type of fibres supply a muscle spindle? | Gamma |
| Usually muscle fibres and spindles are co-activated, what happens when there is only alpha stimulation? | Muscle spindle goes flaccid |
| What happens when there is only gamma stimulation of a muscle? | The gamma stimulation to the muscle spindle causes contraction at either end of the muscle fibre - this causes stretch in the middle which stimulates type Ia and II afferent fibres |
| What do golgi tendon organs give info about? | Tension |
| Muscle sensory receptors give info about movement of the limbs, what do joint receptors give info about? | Position of the limbs |
| What type of receptors are in the joints? Where exactly are they? What afferent fibres do they stimulate? | Mechanoreceptors (Pacinian corpuscles) Ligaments and joint capsules Type II fibres --> dorsal columns |
| What do joint receptors give info about? | Rate of change, movement in joints and limb position |
| What are the three spinal reflexes? | Myotatic, Inverse myotatic and Flexor withdrawal |
| What type of reflex is the myotatic? Explain it | Postural and graded Ia and II fibres go from the muscle spindle through the spinal cord to cause contraction in the muscle fibre. Opposite affect on the antagonistic muscle |
| What type of reflex is the inverse myotatic? | Postural and graded |
| Explain the inverse myotatic reflex | Type Ib fibres go from the golgi tendon organ to two interneurones which inhibit contraction on the muscle fibre (increase in tension = decrease in contraction). The antagonistic muscle is stimulated and it is the opposite effect on the contralateral limb |
| What type of reflex is the flexor withdrawal? Explain it | ALL OR NOTHING (not graded - we can overcome it) Type III and IV fibres take pain signals from the nociceptors to inhibit the extensor muscles and stimulate the flexors. Opposite effect on contralateral limb |
| Give two examples of the myotatic reflex | Knee jerk reflex and biceps/triceps |
| Give an example of the inverse myotatic reflex (ie what would you be doing when this reflex kicked in?) | Lengthens (ie stops contraction) the muscle to prevent damage eg if you were lifting a heavy object |
| Give an example of the flexor withdrawal reflex | When you touch a hot plate and pull your hand back (can overcome it - so you don't drop said plate :P) |
| What is spinal shock? How long do frogs, dogs and humans take to get over it? | When the connection between brain and spinal cord is cut - lose spinal reflexes Frog - few minutes Dog - few days Human - few months |
| If upper motor neurones are between the brain and the spinal cord, where are lower motor neurones? | They come from the spinal cord |
| What are the two types of lower motor neurones? | Alpha and gamma (muscles!!) |
| What are the two types of upper motor neurones? | Pyramidal and extra-pyramidal |
| What are the four extra-pyramidal tracts? | Reticulospinal, Vestibulospinal, Rubrospinal and Tectospinal |
| Explain the inputs and outputs to and from the reticulospinal tract (extra-pyramidal) | Reticular formation --> Reticulospinal tract --> Extensors |
| Explain the inputs and outputs to and from the vestibulospinal tract (extra-pyramidal) | Cerebellum and vestibular apparatus --> vestibular nucleus --> vestibulospinal tract --> extensors |
| Explain the inputs and outputs to and from the rubrospinal tract (extra-pyramidal) | Red nucleus --> rubrospinal tract --> flexors (UNGULATES) |
| Explain the inputs and outputs to and from the tectospinal tract (extra-pyramidal) | Auditory and vision --> tectum --> tectospinal tract --> cervical vertebrae |
| What do the extra-pyramidal tracts control? What are the four types? | Large movements Reticulospinal, vestibulospinal, rubrospinal and tectospinal |
| What is the one type of pyramidal tract? | Corticospinal |
| What is the pathway of the corticospinal tract? | Motor cortex --> corticospinal tract --> spinal cord |
| What does the pyramidal tract control? Do horses have a well-developed pyramidal system? | Fine movement No apart from in their lips (pick up food!!) |
| What are the three types of cuts? What are their function? | Decorticate, decerebrate and spinal To find out the function of the different tracts |
| Ultimately, where do the five tracts (extra-pyramidal and pyramidal) go between? | Motor cortex --> spinal cord |
| Where are central pattern generators (CPGs)found? What are their function? | They are found in the spinal cord They allow an animal with a lesion between it's brain and spinal cord to perform locomotion still |
| Explain indirect contraction | Gamma neurones stimulate contraction at either end of the muscle spindle = stretch in the middle --> stimulate of Ia and II fibres --> MYOTATIC REFLEX --> stimulation of alpha neurones = contraction of muscle fibre |
| What is the function of indirect contraction? | To maintain the flexor angle of a joint - alpha neurones control force, gamma neurones control length = they tell muscle to stay at that particular length even if the load is increasing |
| How do you 'fix' tonic hyperactivity in decerebrate animals? | Cut the dorsal roots |
| What is the positive supporting reflex? (example) | Gravity flexes the stifle joint, stretching the quadriceps muscle, stimulating stretch receptors causing the quads to contract |
| What are the two types of postural reflexes? | Tonic vestibular reflexes and dynamic vestibular reflexes |
| What controls the postural reflexes? | Tonic vestibular reflexes - otolith organs and dynamic vestibular reflexes - semicircular canals |
| What is nystagmus? | Quick flick of the eye eg spinning round - the eyes go round against the direction of the rotation as far as they can then flick back (this happens a couple of times) |
| Eyes give accurate info slowly (vestibular apparatus gives inaccurate info quickly) - explain it when there is no co-operation between the eyes and the vestibular apparatus | If you can't see movement (eyes) but can feel it (vest. app.) eg on a ship/in a car, you get motion sickness (brain thinks you have ingested poison - trying to get rid of it) You can see the movement but can't feel it eg watching TV |
| Explain the neck reflex | Eyes + vest. app. --> vestibular nucleus and cerebellum --> the tonic vestibular reflex stimulates the mechanoreceptor in the neck joint which leads to postural adjustment (muscle spindles + pressure receptors also control this) |
| What happens if the head can't lift up in the neck reflex? | The eyes try and look up (if head is being pushed down) |
| What is the function of the motor cortex? | Controls movement |
| What is Jacksonian epilepsy? | Convulsions start in one finger and spread through the whole body - because epileptic signal starts in one cell then spreads through whole motor cortex? |
| What cranial nerves a) input into the motor cortex and b) carry the output signals from the motor cortex? | a) III and IV b) IV and V |
| What does the motor cortex send info to? | Spinal cord, pons (they send info to cerebellum) and extra-pyramidal tracts --> reticular formation, red nucleus, vestibular nucleus |
| The motor and sensory cortexes are 'beside each other' - what do they exchange info with? | Thalamus |
| What feeds into the motor cortex? | Cerebellum |
| By the way... | ...birds and reptiles don't have a motor cortex :) |
| The cerebellum is the 'old part' of the brain and therefore lesions cause more complex problems - what does the cerebellum do? | Co-ordinates movement |
| What are the two input cells of the cerebellum? Where does their info come from? | Eyes, vest. app., spinal cord --> UNSPECIFIC (PARALLEL) FIBRES Cortex and spinal cord --> olivary nucleus --> SPECIFIC (CLIMBING) FIBRES |
| What are the output cells of the cerebellum? | Purkinje fibres |
| What are Purkinje cells in the cerebellum sometimes referred to and what do they excrete? | Dendrite tree GABA inhibitor |
| GABA (from Purkinje cells - cerebellum) is used where? | Fastigial nucleus --> vestibular nucleus Interpositus nucleus --> red nucleus Dentate nucleus --> thalamus --> motor cortex All 3 --> reticular formation |
| What are the three parts of the cerebellum? What does each control? | Spino-cerebellum (posture) - extra-pyramidal links to spinal cord, vestibulo-cerebellum (eye/head movement) - smallest, cortico-spinal (limb movement) - cortex indirectly linked to spinal cord |
| What are the consequences of problems in the cerebellum? | Intention tremor and overshoot, lose 'stored programmes' |
| What does feedback (cerebellum) entail? | Consciously carry out the first action then feedback (parallel fibres) carries out the rest of the actions automatically such as walking, eating |
| What does the basal ganglia link to? | Thalamus, cortex and cerebellum |
| What are the five areas of the basal ganglia? | Caudate nucleus, Putamen, Globus pallidus, Subthalamus and Substantia nigra First three = corpus striatum |
| What are the consequences of problems in the cerebellum? | Parkinson's = shuffling gait (not muscle problems as they can move normally sometimes eg they can run across the road if a car is coming so it must be neurological) - prob with initiation of movement, unintentional tremor |
| What is ballismus? | Problem with the basal ganglia - unwanted limb movement (opposite to Parkinson's) |
| What is the overall pathway of movement (ie what parts of the brain are involved)? | Basal ganglia (initiates movement) --> Cerebellum (co-ordinates movement) --> Motor cortex (converts to individual commands) --> Spinal cord (cerebellum and motor cortex can go via extra-pyramidal tracts to spinal cord!) |
| Where is the limbic system? | Temporal lobe |
| Humans and primates can store a lot of info in their cerebral cortex as it is not taken up by specific functions - what are they? | Vision, auditory, olfactory, motor and somatosensory |
| What are the three things the limbic system controls? | Motivation, memory and learning, emotion |
| Where is sensory memory stored? | Sensory cortex |
| Where is motor memory stored? | Cerebellum |
| What is central memory? | When you gather info, attach a significance to it and store so you can recall it (certain smell/sight brings back memories!) |
| The hippocampus is the first place targeted by Alzheimers disease - what does it do (memory)? | Converts short-term memory (10 mins) --> long term memory thus a lesion in the hippocampus would allow you to remember things before the lesion but not after |
| What is memory (synapses)? | Increase in number and strength of synapses ie if you use the synapse --> gets stronger --> long term potentiation and if you don't use it --> gets weaker |
| What type of receptor is used in a 'memory synapse'? | Glutamate-NMDA receptor + nitrous oxide communicator (between post- and pre-synaptic fibres) |
| What are animals motivated to do? | Eat, survive and reproduce |
| What are the two types of emotion? | Arousal (fight/flight) and conservation (do nothing - sleep, frieze, hibernate) |
| What controls the emotion rage (fight)? | Amygdala activates it, hypothalamus and septal nucleus inhibits it |
| What controls the emotion fear (flight)? | Amygdala and hypothalamus activates it (lesion on amygdala = animal doesn't show fear when it should) |
| What does the septal nucleus do? | Stops inappropriate behaviour eg a rat getting into a cage with a cat |
| What is the emotion sleep (conservation) controlled by? What is sleep good for? What happens if you don't get enough sleep? | Controlled by reticular activating system, important for memory and you go psychotic if you don't get enough!!!!! |
Created by:
Eilidh
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