Nervous System Outline Health Occupations Nervous System Functions

Nervous System Outline Health Occupations

Nervous System Functions n Directs the functions of all human body systems – 100 Billion Nerve cells n Carry messages from brain to rest of body

Neurons n The basic element of nervous system n Highly specialized n Vary in function, shape, and size n Separated by synapses – Gaps in between each neuron n Neurotransmitters – Stimulates impulse to jump to next nerve

Neurons n 3 Parts – Cell Body § Have fibers to reach out to send or receive impulses – Dendrites § Thin branching extensions of cell body § Conduct nerve impulses to cell body – Axon § Conducts nerve impulses away from cell body § Covered by a myelin sheath – Fatty tissue that makes impulse travel faster § End of axon has fibers that let the impulse leave the nerve

Neurons n 2 Basic Properties – Excitability § Ability to respond to a stimulus – Conductivity § Ability to transmit a signal

Neurons n 3 Types – Efferent (motor) § Carry information to muscles and glands from CNS – Afferent (sensory) § Carry information from sensory system to CNS – Interneurons § Carry and process sensory information

n Neuron bundles = Nerves n Stimulus Receptor Nerve Receptor Impulse

Neuroglias n Support, connect, protect, and remove debris n Do not transmit impulses n Form blood-brain barrier – Permits some chemical substances to reach the brain’s neurons but blocks most others

Central Nervous System (CNS) n Consists of: – Brain – Spinal cord n Center of Control

CNS Functions n Receives and interprets all stimuli n Sends nerve impulses to instruct muscles and glands to take over or respond to certain actions n Causes Voluntary and Involuntary actions

Brain Divisions n Brainstem n Cerebellum n Cerebrum n Diencephalon

n Midbrain Brain Stem – Visual reflexes n Pons – Controls certain respiratory functions n Medulla Oblongata – Regulates heart & lung functions – Swallowing – Vomiting – Coughing – sneezing

Cerebellum n Coordinates musculoskeletal movement – Maintains balance – Posture – Muscle tone

Cerebrum n 2 hemispheres – Left and Right n Cerebral Cortex – Conscious decision making n Four Lobes – Frontal § Moral Behavior, voluntary motor movements – Parietal § Controls and interprets senses and taste – Temporal § Memory, equilibrium, emotion, hearing – Occipital § vision

n Deep Diencephalon portion of brain n Contains: – Thalamus – Hypothalamus n Relay center for sensations n Controls: – Heart rate – Blood pressure – Temperature regulation – Water and electrolyte balance – Digestive functions – Glandular activities

Cerebrospinal Fluid (CSF) n Fills the area between the brain and cranium n Watery fluid that contains various compound n Cradles and cushions brain

Spinal Cord Extends from base of brain to first lumbar vertebrae in back n Protected by: n – – – Cerebrospinal fluid Vertebral column Meninges § 3 layers of membranes that cover brain and spinal cord

Meninges n Dura Mater (outer layer) – Tough, fibrous – Contains channels for blood to enter brain tissue n Arachnoid Mater (middle layer) – Web-like structure n Pia Mater (innermost layer) – Contains blood vessels that nourish spinal cord

Peripheral Nervous System n 12 Cranial Nerves – Carry impulses to and from the brain n 31 pairs of spinal nerves – Carry messages to and from the spinal cord and the torso and extremities of the body

Peripheral Nervous System n 2 Subsystems according to function – Somatic Nervous System – Autonomic Nervous System

Somatic Nervous System n Receive and process sensory input from the skin, muscles, tendons, joints, eyes, tongue, nose and ears n Excite voluntary contraction of skeletal muscles

Autonomic Nervous System n Carry impulses from the central nervous system to glands, various involuntary muscles, cardiac muscle, and membranes n Stimulates organs, glands and senses by stimulating secretions of substances n Divided into sympathetic and parasympathetic divisions

Autonomic Nervous System n Sympathetic – Operates when the body is under stress – Activates responses necessary to react in dangerous or abnormal situations – Fight or Flight response n Parasympathetic – Operates to keep the body in homeostasis under normal conditions

The End