Nervous System

Neuron Classifications

Sensory Neuron: Carries info from a receptor to the CNS

Motor Neuron: Carries commands to effectors

Interneuron: Located in the CNS (reflex center)

Connective Tissue Coverings

Perineurium: Covering around nerve bundles

Endonuerium: Covering around individual nerve fibers (Axons)

Epineurium: Outer covering of a nerve

Multipolar Neurons: Has many dendrites and an axon rising form the cell body: Most neurons with cell bodies in the CNS are multipolar.

Bipolar Neurons:

Unipolar Neurons :

Major Functions of the nervous system:

Integrative function: Coordination of sensory info in the CNS; this info helps decision making

Sensory function: Provided by sensory receptors, which detect internal or external change; info travels from receptors to sensory neurons

Motor function: Nerve impulses conduct along motor neurons to the effectors

Effectors: Muscles/glands that respond to nerve impulses

Tissues

Neuroglia: Cells that support neurons through nourishment, protection, and insulation

Neurons: Cells that communicate through electrical impulses

Axon:Conducts impulses away from the cell body

Axon Hillock: Thickening extension that rises from the cell body

Dendrites: Conduct impulses toward the cell body and provide a receptive service for communication with other neurons

Myelin Sheath: Increases the conduction speed of nerve impulses

Cell Body: Contains major organelles such as the nucleus

Ependymal Cells: Produces cerebrospinal fluid in the CNS

Oligodendrocytes: forms the myelin sheath around axons in the brain and spinal cord

Astrocyte: Lies between blood vessels and neurons

Microglia: Function as phagocytes for bacterial cells and cellular debris, and produces scar tissue

BRAIN

SPINAL CORD

Function

Structure

Spinal cord: Consists of 31 segments that each of which connect to a pair spinal nerves

Lumbar enlargement: A thickened area near the bottom of the spinal cord that provides nerves to the lower limbs

Ascending Tract: Carries sensory info to the brain

Descending Tract: Carries motor info from the brain to muscles or glands

Major Functions: transmit impulses to and from the brain, and house spinal reflex

Cervical enlargement: A thickened area near the top of the spinal cord that provides nerves to the upper limbs

White matter: Made of bundles of myelinated fibers, surrounds a core of grey matter that provides housing to interneurons and neuron cell bodies

Cuada Equina: structure formed near the end of the spinal cord; consists of spinal nerves in lumbar and sacral area

Dorsal root ganglia: Home to the cell bodies of sensory neurons that enter the spinal cord

Posterior and anterior horns: The upper and lower wings of grey matter

Lateral horn: lies between the posterior and anterior horns

Central canal: Contains cerebrospinal fluid and is located in the middle of the gray matter

Spinal Reflexes: Controlled by reflex arcs that pass through the spinal cord

REFLEX ARC

Interneuron: Carries info from sensory neurons to motor neurons

Motor Neuron: Carries info form brain/spinal cord out to an effector

Sensory Neuron: Carries info from a receptor toward the CNS

Effector: Responds to stimulation form a motor neuron and produces a reflex or behavioral action

Sensory Receptor: Detects changes

NEUROTRANSMITTERS: A chemical used to accomplish communication

  • released in response to a nerve impulse
  • more than 100 neurotransmitters exist within the human body
  • composed of acetylcholine, amino acids, and neuropeptides

ACTION POTENTIAL AND THE NERVE IMPULSE

  1. Potassium channels on the axon open
  1. Potassium diffuses outward and repolarizes the axon membrane
  1. Sodium diffuses inward and depolarizes the axon membrane
  1. The action potential causes a local electric current that stimulates adjacent portions of the axon membrane
  1. Sodium Channels on the axon open
  1. A series of action potential occurs along the axon
  1. Stimulus is received
  1. Neuron maintains resting potential

AUTONOMIC NERVOUS SYSTEM

Parasympathetic divisions: Activates under regular, restful conditions(rest and digest).

Sympathetic division: Activates under stressful conditions or in emergencies(fight or flight).

MAJOR DIVISIONS AND SUBDIVISIONS OF THE NERVOUS SYSTEM

PERIPHERAL NERVOUS SYSTEM

CENTRAL NERVOUS SYSTEM

  • Responsible for integration of info and decision making
  • Made up of the brain and spinal cord
  • Contains sensory and motor divisions

MOTOR FUNCTIONS

  • Made up of cranial and spinal nerves that connect the CNS to the rest of the body

Autonomic nervous system: Controls involuntary effectors

Somatic nervous system: Controls voluntary skeletal muscles

Cerebellum: Coordinates muscular activity

Diencephalon : Processes sensory input and controls may homeostatic processes

Brainstem: Coordinates and regulates visceral activities, and connects different parts of the nervous system

Cerebrum: Largest part of the brain; associated with higher brain function, and sensory and motor functions

CRANIAL NERVES

  • The first pair arises from the cerebrum, and the second from the thalamus, but most arise from the brainstem
  • Most are mixed nerves, containing sensory and motor nerve fibers, but some are only sensory, while others are primarily motor
  • The twelve pairs are designated by name and number; the numbers are in order, from superior to inferior
  • There are twelve pairs of cranial nerves that arise from the underside of the brain

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