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The Nervous System. Chapter 48-49. What you need to know!. The anatomy of a neuron. The mechanisms of impulse transmission in a neuron. The process that leads to release of neurotransmitter, and what happens at the synapse. The components of a reflex arc and how they work.

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the nervous system

The Nervous System

Chapter 48-49

what you need to know
What you need to know!
  • The anatomy of a neuron.
  • The mechanisms of impulse transmission in a neuron.
  • The process that leads to release of neurotransmitter, and what happens at the synapse.
  • The components of a reflex arc and how they work.
  • The organization and function of the major parts of the nervous system.
  • One function for each major brain region.
  • The location and function of several types of sensory receptors.
  • How skeletal muscle contracts.
  • Cellular events that lead to muscle contratction
the neuron
The Neuron
  • Functional unit of the nervous system
  • Dendrites: cell extensions that receive

incoming messages from

other cells

  • Axon: transmit messages to other cells
    • Covered in myelin sheath (Schwann cells or oligodendrocytes) to speed up transmission
  • Synapse: is the junction between axons and dendrites
  • Neurotransmitters (NT): chemical messengers (drugs) released from the synaptic terminals of the axon which bind to receptors of the receiver (another neuron, muscle cell, or gland)
    • Acetylcholine, dopamine, serotonin, GABA, etc.
nervous system
Nervous System
  • Central nervous system (CNS) = brain & spinal cord
  • Peripheral nervous system (PNS) = everything else including motor and sensory neurons
  • Nerves are clusters of neurons

Types of neurons:

  • Sensory receptors: receive information from the environment
  • Sensory neurons: send signals from receptors to CNS
  • Interneurons: brain and parts of the spinal cord
  • Motor neurons: transmit signals to effectors (muscles, glands)
action potential nerve impulse
Action Potential (nerve impulse)
  • Membrane potential: difference in electrical charge across the cell membrane
  • Resting potential: neuron at rest (-70mV)
action potential ap
Action Potential (AP)
  • All or none response to stimulus
  • If membrane potential reaches threshold (-55mV) AP will fire
  • Resting state
  • Depolarization
  • Depolarization >= threshold  AP
  • Repolarization
  • Undershoot
  • APs propagate down the axon
  • It jumps from one node of Ranvier to the next (saltatory conduction)
  • The signal is revitalized at every node
  • At the synapse the signal continues via electrical or chemical (NT) stimulus
    • Stimulus can be inhibitory or excitatory
reflex arc
Reflex Arc
  • Simplest response to stimulus
  • Receptor  sensory neuron  interneuron (spinal cord)  motor neuron  effector (reaction)
  • The brain finds out later
central nervous system
Central Nervous System
  • Brain and spinal cord
  • Cells bathed in cerebrospinal fluid (CSF) for nutrients and cleansing
  • Grey matter = neuron cell bodies and unmyelinated axons
  • White matter = myelinated axons
  • Neural glial cells (glia) support neurons:
    • Astrocytes provide nutrients for neurons
    • Oligodendrocytes make myelin sheath in the CNS (Schwann cells in the PNS)
peripheral nervous system
Peripheral Nervous System
  • Divided into two subdivisions:
  • Somatic nervous system: muscles you control
  • Autonomic nervous system: automatic muscle and organ control subdivided into two more categories
    • Sympathetic division: fight or flight mechanism
    • Parasympathetic division: rest and digest
  • Compartmentalized:
  • Brainstem = medulla oblongata, pons, and midbrain
    • Primitive brain = primitive functions like homeostasisand breathing
  • Cerebellum: coordinated motor movement
  • Thalamus: main center for all sensory and motor information
  • Hypothalamus: regulates homeostasis and basic survival behaviors
  • Cerebrum: two hemispheres with grey over white matter
    • Cerebral cortex: Higher order thinking occurs here (largest in mammals) and voluntary movement
  • Corpus callosum: white matter enabling communications of the two hemispheres
sensory receptors
Sensory Receptors

Perception: brain recognition of stimulus

Reception: receptor detects a stimulus

  • Mechanoreceptors: stimulated by physical stimuli
  • Thermoreceptors: stimulated by temperature
  • Chemoreceptors: chemical stimulation (taste and smell)
  • Electromagnetic receptors (photoreceptors): detect various forms of energy (light, electricity, or magnetism)
  • Pain receptors: detect too much heat or chemicals released from dying cells