The Nervous System: Part 2 Lecture PDF

The Nervous System: Part 2 Organization Learning Outcomes for this week Describe the structures and functions of the cerebrum, the cerebellum, the diencephelon, and the brain stem. Describe the connective tissue layers surrounding the brain and spinal cord. Explain the function of the...

The Nervous System: Part 2 Organization Learning Outcomes for this week Describe the structures and functions of the cerebrum, the cerebellum, the diencephelon, and the brain stem. Describe the connective tissue layers surrounding the brain and spinal cord. Explain the function of the cerebrospinal fluid. Learn the cranial nerves (names and numbers will be provided) and their functions. Differentiate between the sympathetic and parasympathetic nervous systems and between autonomic and somatic reflexes. Describe the components of a reflex arc and explain its role. Describe the stretch reflex, withdrawal reflex, palpebral reflex, and pupillary light reflex. CNS = Central Nervous System Canine brain and spinal cord  CNS – what does it contain? Glial cells Neuron cell bodies Myelinated nerve Cross section of spinal cord fibres (axons) Non-myelinated Grey matter nerve fibres Neuron cell bodies (axons) Non-myelinated nerve fibres (axons) Darker brownish/grey White matter Myelinated axons Cross section of sheep brain – caudal half Gross anatomy of various species’ brains  Main sections of the brain – pg 245 Cerebrum Diencephalon - thalamus, hypothalamus, pituitary Brainstem – midbrain, pons, medulla Cerebellum Pituitary  Functions of the main brain parts Cerebrum – intelligence, learning Cerebellum (A) – coordinates motor control Diencephalon – pathway from cerebrum to primitive brain Brainstem – maintains basic life functions - Median section of sheep brain subconscious Which way is rostral? Parts of the cerebrum – NOTE: grey matter on the outside, vision info processed caudally, smell info processed rostrally (don’t worry about the rest) Functions of parts of the cerebrum (just know that different parts of the cerebrum are involved in different inputs and outputs)  Cerebrum Gyri (singular is gyrus) Sulci (sing. sulcus) Corpus callosum – white matter Longitudinal fissure Left and right hemisphere Seizures Spontaneous firing https://www.marvis of neurons in tavet.com/seizure- cerebrum disorder.pml Various causes – toxins, drugs, low blood glucose, idiopathic, tumour, inflammation Cerebellum Cerebellar hypoplasia mild Cerebellar hypoplasia moderately sev ere Gray matter on the Cerebellar hypoplasia severe outside Works with cerebrum’s signals and body’s position Sends efferent signals to fine tune muscle movements (agonist/antagonist muscles) Diencephalon = thalamus, hypothalamus, pituitary gland (not distinct grey and white) Thalamus Relays sensory signals to the cerebral cortex Regulates consciousness, sleep, alertness Hypothalamus How the nervous system talks to the endocrine system Pituitary Receives instructions from hypothalamus, sends messages to rest of endocrine glands Brainstem = midbrain, pons, medulla oblongata Basic support functions of the body (not distinct grey and white) Autonomic cardiac functions Autonomic respiratory functions (coughing, sneezing, hiccups too) Vasomotor control (constriction/dilation of blood vessels) The Meninges dura Arachno pia OUT IN mater id layer mater Meninges – blood vessels in these layers, fluid, fat and CT between layers protects brain, distributes nutrients Arachnoid mater – Dura mater – tough, spider webs in the fibrous CT arachnoid space Meninges Pia mater (orange ) Directly attached to brain and spinal cord Very thin Inflamed? CSF – cerebrospinal fluid Circulates through CNS Cushions, brings nutrients Usually fairly low in protein and low in cell numbers Brain and spinal cord are surrounded by it Also in canals, ventricles CSF tap on a boxer BBB – blood-brain barrier Functional separation of brain from circulation bring things from elsewhere in the body Often, capillaries have spaces between their simple squamous cells Or even fenestrations Capillaries are often very leaky on purpose – not so in the brain! BBB – blood-brain barrier Functional separation of brain from circulation 1) No fenestrations (holes) in capillary walls in brain 2) Tight junctions between capillary endothelial cells 3) Astrocytes also attached to/cover capillaries Only certain molecules,drugs can get across 2 minute BBB explanatio n  Spinal Cord Protected by vertebral canal Between each vertebral pair (i.e. between C1 and C2, between C2 and C3) nerves come out of/into spinal cord – left and right Canine spinal cord in vertebral can Spinal Cord Dorsal horns – neurons that process/carry afferent signals to brain Ventral horns – neurons that process/carry efferent signals to body Dorsal root – sensory (afferent) nerves (pseudounipolar) Ventral root – motor (efferent) nerves PNS – spinal nerves, cranial nerves Ventral aspect of sheep brain showing cranial nerves I - XII Nervous system organization Autonomic Nervous System Sympathetic Parasympathetic Thoracolumbar Cranial-sacral system system Candlelight dinner Candle fell over, table Homeostasis cloth now burning Manages non-alarm state Fast reflexes Recovery after sympathetic Norepinephrine is #1 stimulation neurotransmitter Slower (binds to alpha1, beta1 Ach is #1 neurotransmitter and beta2 adrenergic (binds to nicotinic receptors receptors) and muscarinic receptors) FIGHT OR FLIGHT REST AND DIGEST Autonomic Nervous System Sympathetic vs. Parasympathetic (see Table 9- 3) Reflexes – all have the reflex arc - protective mechanisms Somatic reflexes - involve contraction of skeletal muscles Autonomic reflexes - regulate smooth muscle, cardiac muscle, and endocrine glands (e.g. gastrocolic reflex) Lateral abdominal radiograph of a silly dog - this would stimulate the vomiting reflex, an autonomic reflex Reflex arc – simple stretch (no interneuron) – keeps muscle from over- stretching Sensory info goes through dorsal nerve root to dorsal horn Motor info goes out through ventral horn, then ventral nerve root to contract the same muscle – prevent from overstretching See Stretch Reflex pg 255 Reflex arc – withdrawal reflex – has interneuron synapse – more than one muscle may be signaled to contract, anatagonist muscle may be signaled to relax Clinically important reflexes Cranial nerve exam PLR at 0:48 – Palpebral reflex 2:06 tap medial or lateral canthus Pupillary light reflex for monitoring (PLR) anesthesia shouldn’t blink if fairly deeply anesthetised Palpebral reflex