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Spinal Cord + Brain
WVWC Physiology
| Question | Answer |
|---|---|
| Nerve | is a cord-like organ composed of numerous nerve fibers (axons) bound together by connective tissue |
| General anatomy of a nerve: | Schwann cell = myelin sheath around the axon Each fiber is then surrounded by a basal lamina A thin sleeve of loose connective tissue endoneurium. Nerve fibers (axons) are bundled into fascicles. Several fascicles are surrounded by a perineurium sheath |
| Meninges | three fibrous connective tissue membranes that separate the soft tissue of the CNS from bone. |
| Three layers of Meninges | Dura mater, Arachonoid mater, Pia Mater |
| Dura Mater | superficial, forms a loose fitting sleeve (dura sheath) Space between the sheath and bone is epidural space |
| Arachnoid mater | Middle, simple squamous epithelium adheres to the inside of the dura Subarachnoid space between arachnoid and pia is filled with cerebrospinal fluid (CSF) |
| Pia mater | Deep, delicate translucent membrane that closely follows the spinal cord. The terminal filum fuses with the dura mater and together form a coccygeal ligament anchors the cord and meninges. Regular intervals, extensions of the pia mater called denticula |
| Gray matter of Spinal Cord | Dull color because it contains little myelin.Site of synaptic contact between neurons … so, it’s the site of all synaptic integration in the CNS – info processing.Contains somas, dendrites, and proximal parts to axons |
| White matter of Spinal Cord | Bright pearly white appearance due to abundant myelin Composed of bundles of axons “tracts” that carry signals from one part of the CNS to another |
| Spinal tracts: | Ascending, Descending. |
| Ascending Spinal Tract | carries sensory information up the cord First order neuron … detect a stimulus and send the signal to spinal cord or brain Second order neuron … continues to the thalamus at the upper brainstem Third order neuron … carries signal to sensory region of t |
| Descending | conducts motor impulses down the cord Upper motor neuron … begins at a soma in the brainstem with an axon that terminates on a lower motor neuron Lower motor neuron … axon leads the rest of the way to muscle or target organ. |
| The patellar reflex | requires only a sensory neuron + motor neuron |
| The Withdrawal Reflex | requires a sensory neuron + interneuron + motor neuron |
| Spinal cord | Cylinder of nervous tissue that arises from the brain stem at the foramen magnum of the skull. The cord gives rise to 31 pairs of spinal nerves. |
| Spinal Cord Divided into Four regions | Cervical, Thoracic, Lumbar, Sacral. |
| Two areas where the cord is thicker: | Cervical Enlargement,Lumbar Enlargement |
| Cervical enlargement | nerves of the upper limbs |
| Lumbar Enlargment | nerves of the pelvis and lower limbs |
| Inferior to lumbar enlargement | is the medullary cone … where the cord tapers to a point. |
| Cauda Equina | cone give rise to a bundle of nerve roots from L2-S5 that innervate pelvis and lower limbs |
| Brain Conceptually divided into three main parts: | Cerebrum, Cerebellum, Brainstem |
| Cerebrum | About 83% volume Two half-globes cerebral hemispheres Each has thick folds “gyri”, shallow grooves “sulci” Deep groove “longitudinal fissure” separates the two halves Two halves are connected by a thick bundle of nerve fibers “corpus callosum” |
| Cerebellum | Occupies the posterior cranial fossa, inferior to the cerebrum Also marked by gyri, sulci, and fissures Second largest brain region: 10% volume, but 50% of its neurons |
| Brainstem | Remainder of the brain (excluding cerebrum and cerebellum) Major components: (diencephalon), midbrain, pons, medulla oblongata |
| Gray matter of the Brain | Very little myelin, dull in appearance Forms a surface layer “cortex” over the cerebrum and cerebellum |
| White matter of the Brain | Rich in myelin, pearly white appearance Surrounds deeper masses “nuclei” |
| Pia mater of the Brain | very thin delicate membrane follows the contours of the brain |
| Arachnoid mater of the Brain | Transparent membrane over the brain surface Separated from the pia mater by a subarachnoid space Sometimes separated from the dura by a subdural space |
| Dura mater of the Brain | Outer periosteal layer and inner meningeal layer (continues to spinal cord to form the dural sac) Pressed closely to the cranium, no intervening epidural space In some places, the 2 layers of dura are separated by dural sinuses that collect blood that |
| Cerebrospinal fluid (CSF) | clear, colorless liquid that fills the ventricles and canals of the CNS and bathes its external surface.Brain makes ~500 ml/day, but it’s constantly reabsorbed at the same rate Continually flows in and around the CNS |
| The CSF serves three purposes: Buoyancy | allows the brain to reach a large size without being impaired by its own weight |
| The CSF serves three purposes: Protection | prevents the brain from striking the cranium when the head is jolted. (but, consider concussions or shaken baby syndrome) |
| The CSF serves three purposes: Chemical stability | flow of CSF rinses away wastes from nervous tissues and homeostatically regulates its chemical environment |
| Medulla oblongata | All nerve fibers connecting the brain to the spinal cord pass through the medulla! Contains neural networks involved in fundamental sensory and motor functions |
| Pons | Cranial nerves V-VIII begin or end here and are responsible for sensory roles such as hearing, equilibrium, taste … or motor roles |
| Midbrain | A short segment of brainstem that connects hindbrain to forebrain. Includes cranial nerves III and IV involved in control of eye movements |
| Reticular formation | Loosely organized web of gray matter that runs vertically through all levels of the brainstem |
| Cerebellum | Largest part of the hindbrain, second largest part of the brain as a whole. Consists of right and left cerebral hemispheres connected by a narrow worm-like bridge called the vermis.Deeper layer of gray matter “deep nuclei” surrounded by white matter |
| Thalamus | Filters signals coming in and sends only some on to the cerebral cortex.Plays a key role in motor control by sending signals from the cerebellum to the cerebrum. Also involved in memory and emotional functions. |
| Hypothalamus | Major control center for the autonomous nervous system and endocrine system … playing a critical role in homeostatic regulation of nearly all organs in the body.Extends anteriorly to the optic chiasma where the optic nerves meet. |
| Five anatomically and functionally distinct lobes: | Frontal lobe, Parietal lobe, Occipital lobe, Temporal lobe, Insula. |
| Frontal lobe | voluntary motor functions, motivation, memory, mood, social judgement, aggression |
| Parietal lobe | interprets signals from general senses and some visual processing |
| Occipital lobe | principle visual center in the brain |
| Temporal lobe | hearing, smell, learning, memory, some visual and emotion |
| Insula | deeper than other lobes so less well studied. Some role in understanding spoken language, taste, integrating sensory info from visceral receptors |
| Categorical Hemisphere | Language, reasoning, math, linear analysis |
| Representational Hemisphere | imagination, art, music, spatial relations, senses. |
Created by:
lorette_ca
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