1. DETECTING AND RESPONDING TO SIGNALS

2. 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

3. Neurons receive, conduct and transmit electrical signals.

4. 3 main types of nerve cells
sensory neurone
inter neurone
motor neurone
90% of our neurons are inter neurons

5. TYPES OF SIGNALS PHYSICAL light heat Touch
CHEMICAL – specific signalling molecules nutrient molecules (glucose) hormones neurotransmitters pheromones
ELECTRICAL SIGNALS

6. 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

7. Communication systems
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

8. Negative vs. Positive feedback
Stimulus Receptor Brain/Spinal Cord Effector Response
Negative feedback - response reduces stimulus
Positive feedback - response increases stimulus

9. Action Potentials
The membrane of any nerve cell is polarised Signals 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”

10. “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

11. 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.

12. 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.

13. 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)

15. SIGNALLING ALONG THE NERVOUS SYSTEM
Chemical
Chemical
Electric
Electric
Electric
Synapses

16. Reflex Arc - act first, think later

17. 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