1. Nervous system

2. General Info The nervous system controls movement, reflexes and thought processes The nervous system controls movement, reflexes and thought processes It is composed of simple neurons that conduct electrical impulses to and from, and within the central nervous system (brain and spinal cord) It is composed of simple neurons that conduct electrical impulses to and from, and within the central nervous system (brain and spinal cord) Contains neurons and glial cells (also called neuroglial cells) Contains neurons and glial cells (also called neuroglial cells) Glial cells are non-conducting, provide structural support and are involved in metabolism of nerve cells Glial cells are non-conducting, provide structural support and are involved in metabolism of nerve cells Neurons are the functional unit of nervous system Neurons are the functional unit of nervous system

3. Neurons: functional unit that consists of these: 1.Dendrite: conducts impulses to cell body 2.Axon: conducts impulses away from cell body 3.Schwann cells: increase speed of impulse of conduction, are the makeup of myelin sheath and makes it greyish white in colour 4.Nodes of Ranvier: point of depolarization

5. Types of neurons: 1 sensory neurons Conduct impulse from a sense organ to the central nervous system Conduct impulse from a sense organ to the central nervous system Cell body and dendrite outside of spine Cell body and dendrite outside of spine Have long dendrites, sort axon Have long dendrites, sort axon Called “afferent” neurons. Called “afferent” neurons. Eg: right hand finger tips respond to heat. Eg: right hand finger tips respond to heat.

6. Types of neurons: 2 Interneurons Conduct impulses within central nervous system Conduct impulses within central nervous system Connect sensory neuron with correct motor neuron Connect sensory neuron with correct motor neuron Eg. Makes sure if the right finger feels the heat, the right arm responds, not the left Eg. Makes sure if the right finger feels the heat, the right arm responds, not the left They have short dendrites and long or short axons (grey matter is mostly interneurons) They have short dendrites and long or short axons (grey matter is mostly interneurons)

7. Types of neurons: 3 motor neurons Conduct impulses from central nervous system to a muscle fibre or gland Conduct impulses from central nervous system to a muscle fibre or gland Have short dendrites, long axon Have short dendrites, long axon Called “efferent” neurons Called “efferent” neurons Eg. Right arm muscles pull hand away from heat source Eg. Right arm muscles pull hand away from heat source

9. Brain break!!!

10. Reflex arc If you touch a hot source (feel pain) you pull your and away before the brain is notified If you touch a hot source (feel pain) you pull your and away before the brain is notified Sensory organ  spine  effector Sensory organ  spine  effector Stimulation of sensory neuron causes impulse to be sent to spinal cord Stimulation of sensory neuron causes impulse to be sent to spinal cord Impulse transferred to interneuron Impulse transferred to interneuron Impulse is transferred to correct motor neuron, causing muscle to contract (hand is pulled away) Impulse is transferred to correct motor neuron, causing muscle to contract (hand is pulled away)

12. Nerve impulses Resting potential Resting potential Nerve impulses are produced and conducted as a result of changing ion concentrations inside and outside the neuron Nerve impulses are produced and conducted as a result of changing ion concentrations inside and outside the neuron Normally, there is a charge difference between the inside and outside of the neuron Normally, there is a charge difference between the inside and outside of the neuron

13. Resting potential cont’d Unequal concentration gradient Unequal concentration gradient The outside is positive and the inside is negative (due to relative difference of ions) The outside is positive and the inside is negative (due to relative difference of ions) This creates a voltage difference ( -60 to -70 mV) called the resting potential This creates a voltage difference ( -60 to -70 mV) called the resting potential Resting potential is maintained by the active transport of Na + and K + ions Resting potential is maintained by the active transport of Na + and K + ions

15. Action potential: brought on by stimulus Initially neuron is at its resting potential Initially neuron is at its resting potential Stimulation causes sodium gates to open. Na + ions rush into the neuron, causing inside of neuron (at that point) to be positive = called depolarization Stimulation causes sodium gates to open. Na + ions rush into the neuron, causing inside of neuron (at that point) to be positive = called depolarization Immediately, Na + gate closes, and K + opens and K + ions diffuse out of neuron. Action potential now negative again = called repolarization Immediately, Na + gate closes, and K + opens and K + ions diffuse out of neuron. Action potential now negative again = called repolarization Refractory period: immediately afterwards the axon is unable to respond to stimuli. Na + /K + pumps restore initial concentrations of Na + and K + Refractory period: immediately afterwards the axon is unable to respond to stimuli. Na + /K + pumps restore initial concentrations of Na + and K +

16. Action potential cont’d Resting potential (-60 mV) is restored Resting potential (-60 mV) is restored