SBI 4UJANUARY 14 T H , 2013

The Importance of the Nervous System

Nervous System & Homeostasis

Human brain – control centre of the bodyIf brain is damaged, other parts of your body

effected as wellNervous system, body’s interface with

external environment and the control system that manages the internal environment

Physical, cognitive or physiological changes

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 Signalling

Reception: detectionTransmission: movement of a message Integration: sorting and interpretation,

determining appropriate responseResponse: output or action

Neural Signalling

3 functional classes of neurons:1. Afferent neurons: transmit stimuli to;2. Interneurons: integration info to formulate

response;3. Efferent neurons: carry response signals

to effectors

Neural Signalling

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

Stimulus afferent neurons interneurons efferent neurons effectors action

Neuron Structure

Vary in shape & sizeEnlarged cell body and 2 extensionsCell body (nucleus and most organelles)

synthesizes most proteins, carbs and lipidsDendrites receive signals and transmit

toward cell bodyAxons conduct signals away from cell body to

another neuron or effectorAxon hillockNeuronal circuits

Neuron Structure

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 SystemCNS and PNSCNS: coordinating centre brain and spinal cordPNS: communicates with CNS. SubsystemPNS: afferent system (receives input through receptors)

and the efferent system (carries signals to muscles and glands)

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

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

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