Nervous System Ch. 49
Nervous System 1. Central nervous system (CNS): brain and spinal cord. 2. Peripheral nervous system (PNS): cranial nerves, spinal nerves, and nerves that travel throughout the body.
Ch. 49.1 Neurons & Nerve Impulses Neuron Structure: 1. dendrites 2. cell body (nucleus) 3. axon (axon terminals) 4. synapse (gap) 5. neurotransmitters
Neurotransmitter Function Acetylcholine Muscle contraction throughout the body. Dopamine Emotions, regulate movement.(Parkinson's) Endorphins Natural painkiller, sexual stimulant, reduce stress, feeling of euphoria. Epinephrine Increases heart rate, constricts blood vessels, fight-or-flight response. (adrenaline) Norepinephrine Increases heart rate, increases breathing rate, increases blood flow to skeletal muscles. Serotonin Helps with sleep, ‘happy’ feeling, emotions, relieves depression.
Neurotransmitters
Nerve Impulses Neuron function is dependent upon electrical activity: Resting Potential (Na+ out, K+ in) -neurons are in a state of waiting for a stimulus. Action Potential (Na+ in, K+ out) -dendrites or cell body become stimulated. -ATP driven sodium-potassium pump re-establishes equilibrium (restores the ions to be ready for another action potential)
Ch. 49.2 Structures of the Nervous System
External Brain Cerebrum -two cerebral hemispheres -corpus callosum…heavy band of nerves; connects the two hemispheres -area for sensory processing and motor responses
Lobes of the Brain: Frontal: intellectual function, emotions Parietal: motor and sensation Temporal: hearing Occipital: vision Cerebellum: balance & coordination
Diencephalon 1. Thalamus: -directs incoming sensory & motor signals to the proper area of the cerebrum. -regulates consciousness, sleep, and alertness. 2. Hypothalamus: -maintains homeostasis. -controls hormone production. -controls anger & aggression.
Brain Stem: (links cerebrum with the spinal cord) 1. Midbrain: relays visual, auditory, motor, alertness, and temperature regulation. 2. Pons: relays info between cerebral hemispheres and the cerebellum. 3. Medulla Oblongata: heart rate, breathing rate, blood pressure. Video Clip
Cerebellum: (coordination of muscle activity) Spinal Cord: sensory neurons motor neurons interneurons
Protection for the Nervous System Meninges (layers) 1. Dura Mater 2. Arachnoid Layer 2a. Subarachnoid Space: contains Cerebrospinal Fluid 3. Pia Mater
Divisions of the Nervous System Peripheral Nervous System Central Nervous System Sensory Motor Somatic NS Autonomic NS brain and spinal cord Regulates activities under conscious control Regulates activities that are automatic Parasympathetic – slows down activities Sympathetic – Speeds up activities
Peripheral Nervous System -afferent neurons (towards)…what we call sensory neurons. -efferent neurons (away)…what we call motor neurons. Two divisions: Sensory and Motor.
Division 1: Sensory -contains sensory receptors (nerves) and interneurons that connect them to the brain.
Division 2: Motor 1. Somatic Nervous System -Composed of two independent systems: 1. Somatic Nervous System -controls skeletal muscles -reflexes -mainly voluntary, but can be involuntary.
2. Autonomic Nervous System -Controls smooth muscles in blood vessels and organs; respiration, heartbeat and other homeostatic functions -Two Divisions: 1. Sympathetic (stress…moves blood to appropriate organs based upon the stressor. 2. Parasympathetic (normal)
Ch. 49, section 3: Sensory Systems Mechanoreceptors Photoreceptors Chemoreceptors Thermoreceptors Pain receptors Main sense organs: eyes, ears, nose, mouth & skin