Detecting and responding to signals
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DETECTING AND RESPONDING TO SIGNALS. The communication systems. ENDOCRINE - Chemical messengers secreted by cells and carried via a transport system , finally diffusing into extra cellular fluid surrounding a target cell

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The communication systems
The communication systems

  • ENDOCRINE- Chemical messengers secreted by cells and carried via a transport system, finally diffusing into extra cellular fluid surrounding a target cell

  • NERVOUS- System of specialised cells providing rapid and precise signalling via the transmission of electric impulses


Neurons receive, conduct and transmit electrical signals.


3 main types of nerve cells
3 main types of nerve cells

sensory neurone

inter neurone

motor neurone

  • 90% of our neurons are inter neurons


Types of signals
TYPES OF SIGNALS

  • PHYSICALlightheatTouch

  • CHEMICAL – specific signalling moleculesnutrient molecules (glucose)hormonesneurotransmitterspheromones

  • ELECTRICAL SIGNALS


Receptor types
Receptor types

  • Chemoreceptor

    Detect chemical stimulus: taste, smell, co2 levels, blood glucose levels

  • Mechanoreceptors

    Detect changes in pressure, touch, balance

  • Photoreceptors

    Detect changes in light

  • Thermoreceptors

    Detect changes in temperature

  • Pain receptors

    Free nerve endings in the skin


Detecting and responding to signals

Transmission by nerves

Receptor

STIMULUS

Receive the signals

-physical, chemical, internal or external

Communication systems

-nervous and endocrine systems

RESPONSE

Effectors

Feedback-the stimulus is changed because of the response

Take action in response to the stimulus

Transmission by nerves or hormones


Negative vs positive feedback
Negative vs. Positive feedback

Stimulus Receptor Brain/Spinal Cord Effector Response

Negative feedback- response reduces stimulus

Positive feedback- response increases stimulus


Action potentials
Action Potentials

The membrane of any nerve cell is polarisedSignals are sent along a nerve cell when (+) particles are pumped inside the membrane As (+) ions move inside the membrane, they stimulate neighbouring (+) to following causing a “domino effect”


“all or nothing reaction” a signal will not be sent along an axon unless it reaches approx -55 mV (this is caused by Na+ ions crossing the membrane)

If this threshold is not reached, the neighbouring Na+ ions are not stimulate to cross the membrane, and the signal stops


Refractory period
Refractory Period

  • Brief period of time between the triggering of an impulse and when it is available for another.

    • NO NEW action potentials can be created during this time.


Conduction velocity
Conduction Velocity:

  • impulses typically travel along neurons at a speed of anywhere from 1 to 120 meters per second

  • the speed of conduction can be influenced by:

    • the diameter of a fiber

    • the presence or absence of myelin

  • Neurons with myelin (or myelinated neurons) conduct impulses much faster than those without myelin.


The synapse bridging the gap
THE SYNAPSE “Bridging the gap”

1.Neurotransmitter released upon stimulus from pre synaptic axon

3.Neurotransmitters bind to receptors on dendrite of post synaptic neuron

impulse

impulse

2.Neurotransmitters cross synapse

Neurotransmitters stored in vesicle at the end of axon, released from synaptic cleft through exocytosis (there are various types of neurotransmitters)


Signalling along the nervous system
SIGNALLING ALONG THE NERVOUS SYSTEM

Chemical

Chemical

Electric

Electric

Electric

Synapses


Reflex arc act first think later
Reflex Arc - act first, think later


Reflex arc
Reflex Arc

  • Many of the bodies essential systems operate through reflex arcs (eg. The heart, the liver, the stomach, etc)

  • Fight or Flight responses employ reflex arcs in order to decrease response time

  • The reflex arc involves signals being processed by the spinal cord rather that in the cerebrum, this creates a shorter response time


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