Unit 7 Part 1: The Nervous System

The nervous system controls and coordinates functions throughout the body and responds to internal and external stimuli

Impulses are electrical signals that carry messages through the nervous system

Neurons are nerve cells that transport impulses

Neurons are classified according to the direction in which an impulse travels

Types of Neurons

Sensory Neurons:

They carry impulses from the sense organs to the spinal cord and brain

Motor Neurons:
They carry impulses from the brain and spinal cord to muscles and glands

Types of Neurons Cont.

Interneurons:

Connect sensory and motor neurons and carry impulses between them

Structure of a Neuron

Dendrites: extending from the cell body, they carry impulses from the environment to the cell body
Axon: long fiber that carries impulses away from the body, they end with the axon terminal
Myelin Sheath: insulating membrane that surrounds the axon
Schwan Cells: wrap around the axon

Saltatory Conduction

Saltatory Conduction:
Impulses "Jump" from one node to the next

This process speeds the transition of the impulse along the neuron

The Nerve Impulse

Outside of the resting neuron is a net positive charge
Inside the Neuron is a net negative charge

Resting potential:

Difference in electrical charge across the cell membrane of a neuron at rest

It's maintained by the sodium potassium pump (Na + K)

Action Potential

The action potential (aka nerve impulse) is the reversal or charge along a nerve cell membrane

An impulse begins when a neuron stimulates another neuron or the enviornment

Action Potential

There is a reversal of changes, also known as the Action potential.

As it passes, the negative charge is restored, and returns to the resting potential.

The inside of the neuron temporarily becomes more positive then the outside

Threshold

The strength of an impulse is always the same
Either there is an impulse, or their is not
The minimum level of a stimulus that is required to activate a neuron is called the threshold
Any stimulus stronger than the threshold will produce an impulse
It is a ALL OR NONE principle

Synapse

The Synapse is the location when a neuron transfers an impulse to another cell
Synaptic Cleft: Space between the axon terminal of one neuron and the dendrites of an adjacent cell
Neurotransmitters: chemicals that are contained in vesicles at axon terminals
They are used to transmit the impulse across a synapse
As the two meet, the neurotransmitters are diffused across into the synaptic cleft to send the message
Sodium ions rush across the membrane, stimulating the next cell

Synapse: Simple Overview

1. Impulse is sent across the neuron: called the action potential (aka nerve impulse)

2. Ends at the axon terminal, where it will meet at the next neurons dendrites

3. When they meet, a chemical is released called neurotransmitters that sends the message from the axon to the dendrite

4. Sodium ions rush across the membrane, and will stimulate the next cell

5. If this stimulation exceeds the threshold, a new impulse will begin until the message is sent
6. After all of this, the neurotransmitters are broken down by enzymes or recycled

Organization of the Nervous System

Central Nervous System

relays message, process info, and analyzes information
consists of the Brain and Spinal Cord
The Brain: has meninges, a layer that surrounds the brain and spinal cord

In-between the brain and the meninges is cerebrospinal fluid, which fills the space and acts as a shock absorber

Somatic Nervous System (Part of PNS)

Regulates actions under conscious control
Some are involved with reflexes, like quick automatic responses to stimulus
Reflex Arc: include sensory receptors - sensory neuron - interneuron - motor neuron - and effecter (all of which are involved in a quick response to stimulus
The effector is the muscle or organ that responds to the command of the nervous system

Autonomic Nervous System (Part of PNS)

Regulates involuntary activities
Subdivided into to parts: Sympathetic and Parasympathetic
Sympathetic: heart speeds up, digestive system slows down
Parasympathetic: slows down heart, speeds up digestive system
Both of these systems help maintain homeostasis

9th grade Biology Slide Set on Unit 7 Biology - Part 1, The Nervous System, created by maddyaddyo on 01/06/2016.

0 comments

Unit 7 Part 1: The Nervous System

Types of Neurons

Types of Neurons Cont.

Structure of a Neuron

Saltatory Conduction

The Nerve Impulse

Action Potential

Action Potential

Threshold

Synapse

Synapse: Simple Overview

Organization of the Nervous System

Somatic Nervous System (Part of PNS)

Autonomic Nervous System (Part of PNS)

	Created by maddyaddyo almost 9 years ago