Nervous System Page 203

Nervous System Directs the functions of all human body systems 100 billion nerve cells Divided into two sections ▫Central Nervous System ▫Peripheral Nervous System  Somatic  Autonomic

Neurons Contain 3 parts ▫Cell body ▫Dendrites ▫Axon  Covered by ‘Myelin Sheath’ Two basic properties ▫Excitability – the ability to respond to a stimulus ▫Conductivity – the ability to transmit a signal

Neuroglias Cells in the nervous system ▫Support ▫Connect ▫Protect ▫Remove  Debris from the nervous system Do NOT transmit impulses Form “blood-brain barrier”

Central Nervous System ▫Composed of brain and spinal cord ▫Brain has 4 major divisions  Brainstem  Cerebellum  Cerebrum  Diencephalon

Brainstem Midbrain ▫Visual reflexes Pons ▫Controls respiratory functions Medulla oblongata ▫Regulate heart and lung functions ▫Swallowing, vomiting, coughing, sneezing

Cerebellum Coordinates musculoskeletal movement to maintain posture, balance, and muscle tone

Cerebral cortex ▫Decision making Frontal lobe ▫Voluntary motor movements ▫Emotional expression ▫Moral behavior Parietal lobe ▫Controls and interprets the senses and tastes Temporal lobe ▫Controls memory, equilibrium, emotion, and hearing Occipital lobe ▫Controls vision and various forms of expression Cerebrum

Diencephalon Contains ▫Thalamus ▫Hypothalamus Serves as relay center for sensations Works with the Autonomic nervous system to control heart rate, blood pressure, temperature, electrolyte balance, digestive functions, behavioral responses, and glandular activities

Central Nervous System Cerebrospinal fluid (CSF) ▫Watery fluid- flows in and around brain and spinal cord ▫Cradles and cushions the brain Spinal cord ▫Extends from the base of the brain – L1

Meninges Three layers of membranes that cover the brain and spinal cord ▫Dura mater  Tough, fibrous membrane that contains channels for blood to enter brain tissue ▫Arachnoid membrane  Weblike structure that runs across the space containing CSF ▫Pia mater  Innermost layer, a thin membrane containing many blood vessels that nourish the spinal cord

Peripheral Nervous System 12 pairs of cranial nerves ▫Carry impulses to and from the brain 31 pairs of spinal nerves ▫Carry messages to and from the spinal cord and extremities of the body Somatic Nervous System Autonomic Nervous System

Somatic Nervous System Receive and process sensory input from ▫Skin ▫Muscles ▫Tendons ▫Joints ▫Eyes ▫Nose ▫Ears Excite the voluntary contraction of skeletal muscles

Autonomic Nervous System Carry impulses from the central nervous system to ▫Glands ▫Involuntary muscles ▫Cardiac muscle Sympathetic ▫Operates when the body is under stress Parasympathetic ▫Operates to keep the body in homeostasis