Neuroanatomy II BIOL2051/2052 Past Paper PDF

Neuroanatomy II BIOL2051/2052 Dr. Melissa Andrews ([email protected]) October 8, 2024  Learning Objectives Describe common neuroanatomical terminology and be able to use it appropriately State the 7 main parts of the CNS, and be able to discuss their funct...

Neuroanatomy II BIOL2051/2052 Dr. Melissa Andrews ([email protected]) October 8, 2024  Learning Objectives Describe common neuroanatomical terminology and be able to use it appropriately State the 7 main parts of the CNS, and be able to discuss their functions in general Describe a spinal nerve in terms of origin and role in peripheral (mixed) nerves Discuss spinal reflexes, comparing and contrasting mono- & polysynaptic reflexes Briefly describe the autonomic nervous system Recommended reading: Chapter 1 (Studying the Nervous System in Humans and Other Animals) in Neuroscience, 3rd ed by Purves et al (check later editions for chapter number) Also revise Dr Andrews’ System Physiology lectures Human CNS – Midsagittal view of the brain/he major parts Brain divisions Cerebrum Cerebrum Diencephalon Brain Stem Bra - Midbrain Cerebellum nSi - Pons tem - Medulla Cerebellum Spinal C Spinal Cord ord White Matter and Gray Matter in the CNS Gray matter Cell bodies of neurons reside in the gray matter. It has a pinkish/gray colour in the brain, and is a major component of the CNS. White Matter Myelinated Axons reside in white matter. These axons uroanatomical Terminology Brain planes uroanatomical Terminology rections in the head of a forward looking hum Protection of the CNS: (bone, meninges, CSF) Skull and vertebral column Meninges (Encloses the brain and spinal cord and their blood vessels) 3 protective tissue layers - dura: superficial most and strongest, usually in contact with bone - arachnoid: adhered closely to dura, web-like in appearance - pia: deepest layer, in direct contact with CNS tissue Contains Cerebrospi nal Fluid Protection of the CNS: (bone, meninges, CSF) CSF (cerebrospinal fluid) – clear, cell-free fluid produced by the choroid plexus (ependymal cells) that circulates in the subarachnoid space (the space between the arachnoid and pia mater) ebral Hemispheres - INPUT 2 hemispheres Afferent input to the (neo)cortex comes from a variety of areas: Ascending information from the thalamus Ascending information from the brainstem and other parts of the forebrain, also the hypothalamus Axons travelling between hemispheres (commissural fibres) cting the Cerebral Hemispheres: Corpus Callos Axons travelling between hemispheres (commissural fibres) ebral Hemispheres - OUTPUT Output from the neocortex is excitatory from pyramidal cells (uses excitatory neurotransmitters such as glutamate, etc) All parts of cortex project to thalamus Axons from motor & somatosensory cortices project to basal ganglia Axons project to brainstem (nuclei) and spinal cord Axons project to contralateral hemisphere; axons project to ipsilateral hemisphere NS – Brain Stem Connects the spinal cord to higher centres (cerebrum, cerebellum) NS – Brain Stem Functions: Serves as a conduit for ascending & descending tracts connecting the spinal cord to higher centres (cerebrum, cerebellum) Contains important reflex centres associated with control of respiration, heart rate & blood pressure, and consciousness Cerebellum - Functions - Integrates ascending (proprioceptive) information, feeds back to cerebral cortex to refine movement - Modifies movement (compares sensory information with pre-motor information) Maintenance of upright posture Balance Aids the cerebral cortex in planning sequential movements to make smooth progressions from one movement to the next Synergy of Movement – Motor coordination Maintenance of the tension or firmness (i.e., NS – Cerebellum Cerebellar Input: - Spinal cord - Cerebellar cortex - Vestibular system - Motor systems in neocortex https:// bellspalsycranialnerves.wordpress.com/ 2013/01/13/neuronal-connections-in-the- cerebellum-in-short/ Cerebellar Output: - Vestibular systems - Brain stem - Muscle spindles - Motor and pre-motor NS – 7 major parts Brain divisions Cerebrum Diencephalon Brain Stem - Midbrain - Pons - Medulla Cerebellum Spinal Cord A two-way impulse conduction pathway and reflex centre. 31 pairs of spinal nerves in total: 8 cervical nerves (C1 – C8) 12 thoracic nerves (T1 – S4, S5, Co1 T12) These give rise to the peripheral nerves of the Spinal nerve – sensory neurons (afferent; inhas Each spinal nerve purple) a: a dorsal root (posterior) through which afferent fibres enter, and which contains the dorsal root ganglion* (DRG) with the cell bodies of the afferent fibres. Axon lies in the dorsal root Cell body in the DRG Skin of the back Posterior horn Spinal nerve Skin of limbs and body wall Spinal nerve – motor neurons (efferent; inEach black) spinal nerve has a: a ventral (anterior) root through which the efferent fibres leave. Their cell bodies are within the spinal cord. Dorsal ramus supplies Motor neurons muscles of the (efferent) back Spinal Ventral ramus nerve supplies body wall and limb plexuses Cell body in the anterior grey horn Axon lies in the ventral root exes - Innate/Instinctive behaviour Survival mechanism Inherited (‘hard-wired’), pre-set behaviour that does not require learning, practice, or experience Simplest type of animal behaviour. Performed without conscious thought Usually rapid, automatic/ involuntary responses to stimuli. Usually follow specific pattern Examples: Invertebrates and vertebrates – locate food (foraging behaviour), locate and live in a suitable habitat, escape predators Mammals – knee-jerk reflex (humans), suckling behaviour in nal Cord – Spinal Nerves, Reflexes A single synapse between a sensory Reflex arc = fibre from a muscle and an alpha-motor 1) receptor (site of stimulus) neuron (Rapid 2) sensory neuron (transmits stimulus) response time, 3) integration centre (can be mono or delay) minimal polysynaptic) 4) motor neuron (conducts impulse to effector) 5) effector (muscle or gland) Spinal reflex = somatic spinal reflexes provides information on integrity of the reflex pathway and degree of excitability of the spinal cord DRG Receptor Muscle spindle Innate behaviour in humans? Spinal Cord Reflexes Polysynaptic reflexes: Involves multiple synapses between sensory axons, interneurons, and motor neurons  Interneurons control more than 1 muscle group.  Produce either EPSPs or IPSPs  Example: withdrawal reflex ripheral Nervous System Peripheral Nervous System Sensory Motor (Afferent) (Efferent) Division Division Visceral Motor Somatic Division Motor Division Autonomic Sympathetic Parasympat Enter nervous Division heticDivisio ic system n Controls GI Function! tonomic Nervous System 2 Divisions responsible for the Maintenance of Homeostasis Both systems are continuously active under normal conditions, with each having discreet and independent functions (antagonistic functions!) ANS together with the endocrine system controls the body's internal organs, thus controlling the circulation of Parasympathetic (“rest blood, activity of the and digest”/ craniosacral) gastrointestinal tract and body temperature. Sympathetic (“fight or flight”/ thoracolumbar)