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The Importance of the Nervous System. SBI 4U January 14 th , 2013. Nervous System & Homeostasis. Human brain – control centre of the body If brain is damaged, other parts of your body effected as well

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The importance of the nervous system

The Importance of the Nervous System

SBI 4U

January 14th, 2013


Nervous system homeostasis
Nervous System & Homeostasis

Human brain – control centre of the body

If brain is damaged, other parts of your body effected as well

Nervous system, body’s interface with external environment and the control system that manages the internal environment

Physical, cognitive or physiological changes


Neural signalling
Neural Signalling

Neuron: specialized nerve cell, functioning unit of nervous system

Neural signalling: communication by neurons – process by which an animal responds appropriately to stimuli – reception, transmission, integration and response


Neural signalling1
Neural Signalling

Reception: detection

Transmission: movement of a message

Integration: sorting and interpretation, determining appropriate response

Response: output or action


Neural signalling2
Neural Signalling

3 functional classes of neurons:

Afferent neurons: transmit stimuli to;

Interneurons: integration info to formulate response;

Efferent neurons: carry response signals to effectors


Neural signalling3
Neural Signalling

Efferent neurons that carry signals to skeletal muscles are called motor neurons

Stimulus  afferent neurons  interneurons  efferent neurons  effectors  action


Neuron structure
Neuron Structure

Vary in shape & size

Enlarged cell body and 2 extensions

Cell body (nucleus and most organelles)  synthesizes most proteins, carbsand lipids

Dendrites receive signals and transmit toward cell body

Axons conduct signals away from cell body to another neuron or effector

Axon hillock

Neuronal circuits



Neuron support system
Neuron Support System

Glial cells: structural support and metabolism of nerve cells

Schwann cells, form layers of membrane called myelin sheaths around axons, gaps between Schwann cells, called nodes of Ranvier, expose axon membrane to extracellular fluids  speeds up the rate of electrical impulses

Division and brain tumors


Organization of nervous system
Organization of Nervous System

CNS and PNS

CNS: coordinating centre  brain and spinal cord

PNS: communicates with CNS. Subsystem

PNS: afferent system (receives input through receptors) and the efferent system (carries signals to muscles and glands)


Organization of nervous system1
Organization of Nervous System

Efferent System divided into somatic system (communicates with skeletal muscles) and autonomic system (communicates with smooth muscles and glands)

Somatic system: voluntary (some exceptions)

Autonomic system: involuntary, digestion, secretion by sweat glands, circulation of the blood, etc;


Organization of the nervous system
Organization of the Nervous System

Autonomic System  sympathetic and parasympathetic divisions

Sympathetic: dominates during stress, danger, excitement or physical activity

Parasympathetic: dominates during quiet, low-stress situations, such as relaxation


Reflex arc
Reflex Arc

Neural circuit  5 components: receptor, the afferent neuron, the interneuron, the efferent neuron, and the effector

Reflex arc: travels through spinal cord, but does not require coordination from brain

Ex: when your finger touches a very hot object


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