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The Nervous System. Central Nervous System (CNS) – brain and spinal cord Peripheral Nervous System (PNS) – nerves that communicate to the rest of the.

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Presentation on theme: "The Nervous System. Central Nervous System (CNS) – brain and spinal cord Peripheral Nervous System (PNS) – nerves that communicate to the rest of the."— Presentation transcript:

1 The Nervous System

2 Central Nervous System (CNS) – brain and spinal cord Peripheral Nervous System (PNS) – nerves that communicate to the rest of the body  Somatic NS – voluntary control  Autonomic NS – involuntary control Parasympathetic division – rest and digest Sympathetic division – fight or flight

3 Neurons Smallest functional unit of the nervous system (specialized cell) Consists of:  Cell body – nucleus/organelles  Dendrites – receive messages  Axons – transmit messages away Usually covered by myelin sheath  Insulates and speeds up impulse

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5 Sensory neurons – transmits info from sensors to the CNS for processing Motor neurons – transmit signals to effectors like muscles and glands Interneurons – connect sensory and motor neurons Nerves – bundle of neurons

6 Nerve Impulse Caused by changes in the membrane potential of a neuron  Membrane potential – difference in electrical charge across a cell membrane At resting potential, the outside of the membrane is positive, while the inside is negative  Concentration of Na+ is higher outside and K+ is higher inside

7 Resting Potential

8 Action Potential Also called a nerve impulse An all or none response to depolarization of the membrane Threshold – minimum level of depolarization needed to generate an action potential

9 Action Potential A stimulus opens voltage-gated sodium channels and Na+ ions enter the cell, making the membrane potential positive  If threshold is reached, action potential is triggered Additional nearby channels open and the membrane potential is changed in the next region of the neuron

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11 Action Potential Membrane potential is restored to resting by the inactivation of the Na+ channels and by the opening of voltage-gated K+ channels which increases K+ leaving the cell AP are propagated along the axon  Saltatory conduction – jumping of nerve impulse between nodes of Ranvier (non-insulated portions) Impulse animation

12 Synapse Junction between two neurons  Could be between neuron and muscle or gland Neurotransmitters – chemical messengers released from synaptic terminals (axon ends)  Diffuse across synapse and bind to receptors on the dendrites of the next neuron  Continues the impulse  May be excitatory or inhibitory  Examples: acetylcholine, dopamine, serotonin, epinephrine, norepinephrine

13 Synapse animation Synapse animation

14 Reflexes A simple automatic nerve circuit in a response to a stimulus  Called a reflex arc  Usually skips the brain and goes from sensory receptor to spinal cord and from spinal cord to the effector like a muscle

15 Sensory Receptors Mechanoreceptors – physical stimuli like pressure, touch or sound Thermoreceptors – heat or cold Chemoreceptors – solute concentration like taste and smell Electromagnetic receptors – EM energy like light, electricity, and magnetism Pain receptors – respond to damage or inflamed tissues due to extreme heat, pressure, or certain chemicals

16 Other Parts… Cerebrospinal fluid (CSF) – bathes nerve cells in fluid, removes wastes, and cushions brain and spinal cord Gray matter – mainly neuron cell bodies and unmyelinated axons White matter – mostly myelinated axons giving the “white” appearance

17 Glial cells or Glia Neuron supporting cells that don’t conduct impulses  CNS Astrocytes – provide physical and nutritional support Microglia – phagocytic for clean up and protection Oligodendrocytes – form myelin sheaths in CNS Ependymal cells – involved in creation and secretion of CSF  PNS Schwann cells – form myelin sheaths in PNS Satellite cells – help regulate external chemical environment

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19 Parts of the Brain Brainstem – Homeostatic functions like breathing rate, heart rate and blood pressure  Consists of medulla oblongata, pons, and midbrain Cerebellum – motor coordination, posture, and balance

20 Cerebrum (cortex)  Higher brain functions like thought and action  Divided into 2 hemispheres with gray matter over white matter Connected by a bundle of axons called the corpus callosum

21  Also divided into four lobes: Frontal – thinking, memory, behavior, and movement Parietal – language and touch Occipital - sight Temporal – hearing, learning, and feelings

22 Limbic System  Buried within the cerebrum  Contains the thalamus, hypothalamus, amygdala, and hippocampus  Controls basic emotions and drives


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