The Nervous System

Ch. 35

The Nerve Impulse

1. The Resting Neuron: -Sodium-potassium pump is moving Na out of the cell and K into the cell.

-This creates a negative charge inside the cell and a positive charge outside the cell.

-This is called resting potential.

2. The Nerve Impulse or Action Potential Begins:

-An ‘electrical stimulus’ starts a nerve impulse.

-The stimulus travels from dendrite to cell body to axon to axon tips.

-Protein channels open; Na flows into the cell and K flows out of the cell.

-This creates a positive charge inside the cell and a negative charge outside the cell.

-This is called an action potential.

3. The Nerve Impulse or Action Potential Continues:

-The impulse travels down the axon in a chain reaction type pattern.

-Na into the cell, K out of the cell.

4. The Impulse Reaches the Axon Tips:

-When the impulse reaches the axon tips (terminal), neurotransmitters are released across the synapse and the impulse continues in the next neuron.

-The sodium-potassium pump moves Na out of the cell and K back into the cell restoring the resting potential; the cell is now ready for the next electrical impulse.

-This all happens in just fractions of a second!

The Synapse & Neurotransmitters

-The electrical impulse travels from dendrites, cell body, and to the axon.

-Neurotransmitters are chemicals that pass the electrical impulse across the synapse.

Ch. 35.3 Divisions of the Nervous System

1. Central Nervous System (CNS)- control center of the body; relays, analyzes, and processes information.

2. Peripheral Nervous System (PNS)- receives information from the environment and relays commands from the CNS to the organs and glands of the body.

CNS Structures- brain and spinal cord.

Meninges- protective layers that surround the brain and spinal cord.

Cerebrospinal Fluid- fluid that protects the brain and spinal cord.

External Structures of the Brain:-The Cerebrum has a right and left hemisphere and is divided into four lobes. -The right and left hemispheres are connected by the corpus callosum.

1. Frontal Lobe- speech, smell, intellect, motor

2. Parietal Lobe- sensory (taste) and spatial recognition

3. Occipital Lobe- vision

4. Temporal Lobe- hearing

Cerebellum- balance and coordination

Brain Stem- connects the brain to the spinal cord; consists of the pons and medulla oblongata.

Pons- relay center between the spinal cord and the brain.

Medulla Oblongata- controls heart rate, respiration rate, and blood pressure.

Thalamus receives sensory information and relays it to the proper area of the cerebrum for processing.

Hypothalamus is the control center for recognition of hunger, thirst, fatigue, anger, and body temperature. It also controls the endocrine system.

The spinal cord is an extension ofneurons from the brain that branchoff to various organs and glandsthroughout the body.

PNS Structures- neurons that run throughout the body. (sensory and motor)

Peripheral Nervous System1. Sensory Division

2. Motor DivisionSomatic- voluntary control

Autonomic- involuntary controlSympathetic- body is under stress.

Parasympathetic- body is at rest.

Ch. 35.4 The Senses

Sensory Receptors- neurons that react to an external stimulus and send the stimulus to the brain.

Types:painthermomechanochemophoto

The Five Senses:

Vision- being able to sense light.

Hearing & Balance- being able to hear and maintain balance (equilibrium)

-semicircular canals (fluid and tiny hairs)

Smell- being able to detect chemicals through the nose.

Taste- being able to detect chemicals through the mouth.

Touch- being able to detect temperature, tactile, and pain; receptors found all over the body (skin).