Nervous SystemCh. 49

Nervous System-Found in every part of the body from the head to the tips of the fingers and toes. -Divided into central nervous system (CNS) and peripheral nervous system (PNS).-CNS contains brain and spinal cord.-PNS contains cranial nerves, spinal nerves, and nerves that travel throughout the body.

Ch. 49.1 Neurons & Nerve Impulses

Neuron Structure:1. dendrites2. cell body3. axon (axon terminals)

4. synapse5. neurotransmitters

Neurotransmitters

Nerve ImpulsesNeuron function is dependent upon electrical activity:

Resting Potential

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

BrainFunction

Structure:1. Cerebrum

two cerebral hemispheres

cerebral cortex…sensory processing and motor responses.

corpus callosum…heavy band of nerves; connects the two hemispheres

white matter…contains axons of cortical neurons.

Lobes of the Brain:

Frontal: intellectual function

Parietal: motor and sensation

Temporal: taste & hearing

Occipital: vision

Cerebellum: balance & coordination

Diencephalon

1. thalamus (directs incoming sensory signals to the proper region of the cerebral cortex)

2. hypothalamus (maintains homeostasis, hormone production)

Limbic System: structures within the brain that control emotions, memory, and motivation.

3. Brain Stem: (links cerebrum with the spinal cord)

1. midbrain (relay center for visual & auditory information)

2. pons (relay center between cerebral hemispheres and the cerebellum )

3. medulla oblongata (heart rate and respiration)

-reticular formation (network of neurons helping to control respiration and circulation and serves as a filtering system for incoming sensory signals.

4. cerebellum: (coordination of muscle activity)

5. spinal cord: sensory neuronsmotor neuronsinterneurons

Divisions of the Nervous System

Central Nervous SystemPeripheral Nervous System

brain and spinal cord Somatic NS Autonomic NS

Regulates activities that are automatic

Regulates activities under conscious control

Parasympathetic – slows down activities

Sympathetic – Speeds up activities

Sensory Motor

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

-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

MechanoreceptorsPhotoreceptorsChemoreceptorsThermoreceptorsPain receptors

Main sense organs: eyes, ears, nose, mouth & skin