The Nervous System OCR Mammalian Physiology and Behaviour A2 Revision

The Nervous System Describe the organisation of the nervous system Outline organisation of autonomic nervous system Outline the role of the autonomic nervous system in digestive system, heart action and the size of the pupil in the eye Structure of the human brain Functions of the cerebrum, hypothalamus, cerebellum, medulla oblongata Symptoms and causes of Alzheimer's disease

Human Nervous System Neurones –Cell body –Nerve fibres –3 types –Motor, intermediate (relay), sensory Glial cells –Schwann cells –Myelin sheath (node of ranvier) Organisation of human nervous system –Central nervous system –Peripheral nervous system

Human Nervous System

Central Nervous System Neurones receive and integrate information arriving via synapses Excitatory and inhibitory synapses Action potential (CC) –Energy from stimulus causes temporary and local reversal of the resting potential (depolarised)

Central Nervous System Brain Spinal cord –Grey and white matter –Cerebrospinal fluid Meninges

Spinal Cord, showing Neurones in a Reflex Arc

Peripheral Nervous System Sensory neurones Motor neurones Spinal nerves Cranial nerves Somatic and autonomic nervous system Somatic nervous system

Autonomic Nervous System Includes all motor neurones that take information to viscera, controlling –Activity of all smooth muscle –Beating of cardiac muscles –Activity of endocrine glands

Sympathetic Nervous System “Fight or Flight” Cell bodies on motor neurones in autonomic ganglion Axons pass to all organs in the body Synapse with smooth and cardiac muscle Noradrenaline (epinephrine) Some use acetylcholine

Parasympathetic Nervous System “Rest and Digest” All nerve pathways begin in the brain, or spinal cord Carry impulse to inside the wall of the organ Synapse with effector organ Vagus nerve carries information to all of organs in thorax and abdomen Acetyl choline

Examples of control by Autonomic Nervous system The digestive system  walls of digestive system have nervous ending from SNS and PSNS –SNS Reduce peristalsis, sphincters close –PSNS Sphincter muscles open, smooth muscle contracts Increase secretions Action of heart –Cardiac muscles are myogenic –SAN –SNS increases rate and force of contraction

Examples of control by Autonomic Nervous system Pupil in the eye –Stimulation SNS Radial muscles contract Widening pupil –Stimulation PSNS Circular muscles contract Narrow pupil

The Brain How do we perceive, think, learn and remember? What exactly is consciousness? How does brain control behaviour such as walking and talking, our emotions? Study of brain –Broca –Study of people with damaged brains

The Brain (continued) Effects of drugs on the brain Brain scans –Computer Assisted Tomography –Positron emission tomography –Magnetic resonance imaging

The structure of the brain

Brain – in situ

Brain and association areas

Functions of cerebrum Higher order processes Cerebral cortex receives sensory information and processes this information Two hemispheres receive information from different sides of body Primary sensory areas Association areas –Parietal, temporal and occipital lobes –Prefrontal association

Functions of hypothalamus Receives and integrates information Brings about responses through Autonomic nervous system or secretions of the pituitary gland Control of body temperature Control of hormones from endocrine glands –Secretions from posterior pituitary gland –Secretions from anterior pituitary glands

Functions of cerebellum Control and co-ordination of movement and posture Involved in learning of tasks requiring carefully co- ordinated movements

Functions of medulla oblongata Control of breathing –Rhythmic patterns of impulses –Conscious controls of breathing patterns –CO 2 receptor cells in Med. Ob. increase frequency of nerve impulses Heart rate and blood pressure –Impulses from M.Ob. to SAN –PSNS (vagus nerve) – SAN beats more slowly –SNS – SAN beats faster

Alzheimer’s Disease Dementia Alzheimer's –Tissues in cerebral cortex looks abnormal –“tangles” –“plaques” Diagnosis –Changing pattern of behaviour

Alzheimer’s Disease Causes –Tau –Beta amyloid –APP –“familial” Alzheimer’s –Environmental factors Prevention and treatment –Symptoms temporarily reduced by drugs –Development of inhibitors –Vaccines –Advice