Nervous System Flashcards
2 Divisions of the Nervous System?
- Central Nervous System (CNS)
- Peripheral Nervous System (PNS)
Central Nervous System (CNS)
- “command centre”
- Brain and spinal cord
- Processes and integrates info
Peripheral Nervous System (PNS)
- Consists of:
- Cranial nerves
- To/from brain
- Spinal nerves
- To/from spinal cord
- Cranial nerves
- 2 divisions of PNS:
- Sensory/afferent division
- Has sensory receptors that detect stimuli (change in internal or external
environments)
- Has sensory receptors that detect stimuli (change in internal or external
- Motor/efferent division
- Nerves convey impulses away from CNS
- Innervates (supplies nerves to) effectors = muscles and glands (endocrine or exocrine)
- Sensory/afferent division
Relationship between CNS and PNS
Receptors (Detect stimuli)
↓ (PNS - afferent, Sensory neurons)
CNS (Integrate)
↓ (PNS - efferent, motor neurons)
Effector (Executes response - muscles + glands)
Peripheral Nervous System
Sensory
↓
Central Nervous System
↓
Motor
↓
Somatic or Autonomic
↓
Sympathetic or Parasympathetic
What are the 2 cell types?
- Neurons
- Neuroglia (glial cells)
Neurons
- Conduct impulses
- Make up CNS and PNS
- Mostly amitotic (irreplaceable)
- Exceptions = taste, olfaction, memory
Structure of Neurons
- Cell body
- Processes from cell body
Cell Body
- Typical organelles
- RER called - Nissl Bodies
- Groups/clusters in CNS = nuclei (gray matter)
- Groups/clusters in PNS = ganglia
Processes from cell body
- Dendrites
- Receive incoming messages and relay to cell body
- Axon
- Carry impulses away from cell body
- Axon hillock = where axon meets cell body
- Axon terminal = typically branched with synaptic end bulbs (enlarged tips)
- May be:
1. Myelinated
2. Unmyelinated
- No myelin
Myelinated
- Wrapped in many layers of cell membrane from Schwann cells (PNS) or oligodendrocytes (CNS)
- Electrical insulation
- Gaps in myelin sheath are called Nodes of Ranvier
- Myelinated axon bundles in:
- CNS = tracts (white matter)
- PNS = nerves
Neuroglia (glial cells)
- Support neuron cells = can undergo mitosis (prone to cancer – brain tumor)
- Types:
- CNS neuroglia
- PNS neuroglia
CNS neuroglia
- Oligodendrocytes
- Microglia
- Astrocytes
- Ependymal – neural epithelia
Oligodendrocytes
Produce myelin around axon
Microglia
- Protective
- Become phagocytic if detect infected, dead, or
damaged neurons (because immune cells can’t enter CNS
- Become phagocytic if detect infected, dead, or
Astrocytes
- Surround blood capillaries to form part of blood brain barrier (BBB)
- Help control capillary permeability
Ependymal – neural epithelia
- Line brain ventricles and central canal of the spinal cord
- Secrete cerebrospinal fluid (CSF) and circulate it (cilia)
PNS neuroglia
- Schwann cells
- Form myelin around axons in PNS
- Satellite cells
- Surround neuron cell bodies in ganglia – protection and support
Neuron Classification
- Structural/Anatomical types
- Functional types
Structural/Anatomical types
- Based on # of cell processes off of cell body
- Unipolar
- Bipolar
- Multipolar
Unipolar
- 1 process that divides into two: central and peripheral
- Peripheral end has dendrites = sensory receptors (pain, touch etc) -
remainder is axon - Always sensory
Bipolar
- 2 processes: 1 axon, 1 process with dendrites
- Sensory – retina, nose (olfaction)
Multipolar
- 3 or more processes: 1 axon, many dendrites
- All interneurons and motor neurons
Functional types
- Based on direction of impulse conduction
- Sensory/Afferent Neurons
- Interneurons
- Motor/Efferent Neurons