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