A+P Nervous System Flashcards
CNS
-Brain
-Spinal cord
PNS
-12 cranial nerves
-31 spinal nerves
Neurons
-Specialized cells that carry “messages” through an electrochemical process
-Brain has around 100 billion
Neurons have specialized extensions called
-Dendrites
-Axons
Dendrites
-Info to cell body
-Rough surface (dendritic spines)
-Many dendrites per cell
-Ribosomes
-No myelin insulation
-Branch near cell body
Axons
-Info away from cell body
-Smooth surface
-Generally only one axon per cell
-No ribosomes
-Can have myelin
-Branch further from the cell body
Neurons communicate with each other through an
Electrochemical process
Neurons contains some specialized structures and chemicals
-Synapses
-Neurotransmitters
Irritability
Ability to respond to stimuli
Conductivity
Ability to transmit an impulse
Bipolar neurons
-2 processes extending from the cell body
-EX: retinal cells, olfactory epithelium cells
Pseudounipolar or unipolar cells
-2 axons rather than an axon and dendrite
-One axon extends centrally toward the spinal cord, the other extends toward the skin or muscle
Multipolar neurons
-Many processes extending from cell body
-Although only one of these is the axon
Neuroglial cells
-Non neuronal cells that provide support and nutrition, maintain homeostasis, form myelin, participate in signal transmission in the NS
-the glue
-Insulation
-Destroy pathogens and remove dead neurons
Differences in glial cells
-Neurons have 2 processes called axons and dendrites
-Glial cells only have one
-Neurons can generate action potentials
-Glial cells cannot (but they do have a resting potential)
-Neurons have synapses that use neurotransmitters
-Glial cells do not have chemical synapses
-Neurons do not continue to divide
-Glial cells do continue to divide
-10 to 50 times more glial cells compared to # of neurons
Supporting cells of PNS
-Schwann
-Nodes of ranvier
-Satellite
Schwann cells
-Successive wrapping of the cell membrane form the insulating myelin sheath
-The outer surface encased in glycoprotein basement membrane which forms the sheath of schwann
Nodes of ranvier
-Unmyelinated areas between adjacent schwann cells
-Nerve impulses are generated at these areas
Satellite cells
Support neuron cell bodies within ganglia
Supporting cells of CNS
-Oligodendrocytes
-Microglia
-Ependymal cells
Oligodendrocytes
-Provide the insulation (myelin) to neurons in the CNS
-Each has extensions that form insulating myelin sheaths around several axons
Microglia
Phagocytes, migratory
Ependymal cells
Line ventricles and secrete CSF
Astrocytes
-Most abundant glial cell
-Star shaped cells that provide physical nutritional support for neurons
-Clean up brain “debris”
-Transport nutrients to neurons
-Hold neurons in place
-Digest parts of dead neurons
-Regulate content of extracellular space
How neurons work (5 steps)
- reception
- transmission
- data interpretation
- transmission
- response
Reception
Receptors in the skin sense stimuli
Transmission (2)
Sensory neurons transmit the touch message
Data interpretation
Information is sorted and interpreted
Transmission (4)
Motor neurons transmit a response message to a muscle
Response
Muscles are activated causing a response
Impulse transmission
-Start with a resting neuron; one NOT transmitting an impulse
-Plasma membrane controls [] of ions inside the cell
-Na+ and K+ on both sides of membrane
-Na+ higher conc outside
-K+ higher conc inside
How an impulse travels
-Stimulus excites a neuron
-Na+ channels open, Na+ build up inside
-Inside more + than outside
-Change in charge (depolarization)
-Membrane immediately behind depolarization returns to resting state
-Resting state: inside neg, outside pos
Resting state
-A neuron is not conducting an impulse
-The K+ concentration is much higher inside the cell than out
-The Na+ concentration is much higher outside the cell than in
Depolarization
-A nerve cell is stimulated
-Membrane becomes permeable to Na+ for an instant and they quickly move into the cell
-The inner surface of the cell membrane is now more positively charged than the outside
Repolarization
When the cell membrane becomes depolarized, K+ automatically leaves the cell until the cell is back to its resting state
The impulse travels
-“Wave” of depolarization: transmission of an impulse along length of axon
-All or nothing threshold
-Covered by myelin sheath
-Myelin sheath causes the ion exchange to occur only at the nodes which speeds up the process
-For a short time after, depolarization, the neuron cannot be stimulated
Brain is wrapped in 3 layers of connective tissue = ?
meninges
Innermost layer
-Pia mater
-Covers/bound to surface of brain; fibrous layer
Arachnoid
-Thin, elastic, weblike layer between pia mater and dura mater
Outer layer
-Dura mater
-Thick connective tissue
Between the pia mater and the arachnoid
CSF
CSF
Clear liquid that protects the brain from mechanical injury by acting as a shock absorber
Cerebrum
-Responsible for higher mental functions
-Control center
-Voluntary/conscious activities of body
-Corpus callosum: major tract of axons that functionally interconnects right and left cerebral hemispheres
-Ridges = gyri
-Grooves = sulcus
-Contains thick layers of unmyelinated neurons = gray matter
Folded outer surface of cerebrum
Cerebral cortex (consists of gray matter)
Inner surface of cerebrum
Cerebral medulla (made up of myelinated axons = white matter)
Left hemisphere of cerebrum
Analytical and mathematical ability
Cerebellum
Coordinates muscle movements, controls balance, posture, coordination
Brain stem
-Serves as the place of entry or exit for 10/12 cranial nerves
-Lowest part = medulla oblongata
-Controls involuntary functions: breathing, BP, HR, digestion, swallowing, coughing
Above medulla
Pons
Above pons
Midbrain
Midbrain
Hearing and vision
Thalamus
-Switch station for sensory input
-Epithalamus contains choroid plexus where CSF is formed
-Immediately below thalamus is hypothalamus
Pituitary gland
-Ant. pituitary: regulates secretion of hormones of other endocrine glands
Sensory input and motor output
PNS
Sensory input
Sensory (afferent) signals picked up by sensory receptors, carried by nerve fibers of PNS to the CNS
Motor output
Motor (efferent) signals are carried away from the CNS, innervate muscles and glands
PNS efferent division
Transmits impulses from receptors to the CNS
Somatic afferent fibers
Carry impulses from skin, skeletal muscles, and joints
Visceral afferent fibers
Transmit impulses from visceral organs
PNS efferent division
Motor (efferent) division: transmits impulses from the CNS to effector organs
2 subdivisions
Somatic NS
Provides conscious control of skeletal muscles
Autonomic NS
Regulates smooth muscle, cardiac muscle, and glands
Proprioceptive senses
Detect stretch in tendons and muscle provide information on body position, orientation and movement of body in space
General somatic motor
Signals contraction of skeletal muscles
Voluntary control
Visceral motor
Makes up autonomic NS
Regulates the contraction of smooth and cardiac muscle, controls function of visceral organs
ANS 2 divisions
Parasympathetic and sympathetic
Sympathetic
Fight or flight
Parasympathetic
-Feed and breed
-Rest and digest
-Relaxing effects: decreases HR, dilates visceral blood vessels, increases digestive activity
