Nervous System & Eye Infections Flashcards
what is the nervous system composed of and what is it divided in
brain, spinal cord and nerves
- divided into Central Nervous System (CNS) & Peripheral Nervous System (PNS)
what does the CNS consist of?
Brain and spinal cord
what does the PNS consist of and what is its function
network of nerves that connect the rest of the body to the CNS
- Function: responsible for communicating between CNS and the rest of the body by collecting info from sensory neurons (Sensory Organs) and motor neurons ( muscles and glands)
what is the function of the nervous system?
to coordinate and send signals from one cell to another and from one body part to another
what are the names of the layers that make of the meninges? what is the meninges?
- Dura mater, archnoid mater, pia mater
- the meninges are the layers of tissue that surround the brain
the PNS can be further divided into other systems, what are they?
Somatic Nervous System (SNS)
Automatic Nervous System (ANS)
what is the
what is the function of the Somatic Nervous System (SNS)
part of the PNS
Function: transmits impulses from receptors to CNS and from CNS to skeletal muscles
the automatic system can be divided into further categories, what are they?
Sympathetic system: spinal nerve only
Parasympathetic system: spinal and cranial nerves
what does the sympathetic system consist of and what does it control?
part of the Autonomic nervous system, it controls the “rest and digest” and contains only spinal nerves
Controls:
- constrict pupils
- stimulate saliva
- slow heartbeat
- constrict airways
- stimulate activity of stomach
- inhibit release of glucose; stimulate gallbladder
- stimulate activity of intestine
- contract bladder
- promote erection of genitals
what does the sympathetic system control
part of the automatic nervous system. consist of spinal nervous only
Controls: fight or flight
- dilate pupils
- inhibit salivation
- increase heartbeat
- releax airways
- inhibit activity of stomach
- stimulate release of glucose’inhibit gallbladder
- inhibit activity of intestines
- secrete epinephrine and norepinephrine
- relax bladder
- promote ejaculation and vagina contractions
what are the functions of the meninges?
- protect the brain and spinal cord from mechanical trauma
- support blood vessels
- form continuous cavity in which cerebral spinal fluid (CSF) passes
describe the spinal cord pathway
the cerebrum sends an impulse down the spinal cord. the impulse is then directed by an interneuron which directs signal to motor neuron that connects to muscles in the arm. motor neuron carries impulse to receptors in arm muscle and when the receptors are stimulated by impulse the arm moves
cerebrum sends impulse⇒interneuron⇒motor neuron⇒receptors⇒effector
what are the types of cells in the nervous system?
Neurons
Neuroglia (supportive cells)
what is the function of a neuron and what are its different parts?
Function: cells the receive and transmit information in the nervous system
Parts:
- Dendrites: branch extension from body, they receive signals from other neurons
- Soma: body, life support center
- Axon: covered in myelin sheath, sends message away from cell body to other neurons
- Terminal branches of axon: branched ending of axon, forms junctions with other neurons
Glial Cell
hold neurons in place, provide nutrition, remove waste products and prevent harmful substances from passing the blood-brain barrier
neurotransmitters
made by the brain and consumer artificially through Rx
can be Excitatory (increase neuron firing) or inhibitory (decrease neuron firing)
how do nuerons communcate
signal is sent from one neuron to the next
Acetylcholine (ACh)
A neurotransmitter
Function: enables muscle action, learning and memory
Dopamine
a nuerotransmitter
influences movement, learning, attention, and emotion
Serotonin
A neurotransmitter
affects mood, hunger, sleep and arousal
Norepinephrine
A neurotransmitter
helps control alertness and arousal
GABA (gamma-aminobutyric acid)
a neurotransmitter
major inhibitory neurotransmitter
Glutamate
a neurotransmitter
a major excitatory neurotransmitter that is also involved in memory
what does the blood-brain barrier consist of?
tightly joined endothelial cells that are surrounded by glial processes
what does the brain- CSF barrier consist of?
at choroid plexus consists of endothelium w/fenestration and tightly joined choroid plexus epithelial cells
How can microbes cross the blood-brain barrier and the blood-CSF barrier?
- growing across which infect cells that make those barriers
- being passively transported across via intracellular vacuoles
- being carried across by infected WBC
what are the portals of infection of the CNS? (4)
- intracellular (paracellular): use of microbial virulence factors, toxins, or inflammation-mediated process to pass between the cells of blood-brain barrier
- transcellular: passage through cells of blood-brain barrier using virulence factors that allow it to adhere and trigger uptake by vacuole or receptor-mediated methods
- leukocyte facilitated: trojan horse, pathogen infects peripheral blood leukocytes to directly enter CNS
- nonhematogenous entry: allows pathogen to enter brain w/o encountering the blood-brain barrier. this is accomplished when pathogen travels along the olfactory or trigeminal cranial nerve that lead directly to CNS
how does the body respond to the invasion of the blood-brain barrier?
- increase in CSF cell count
- response to invading viruses cause increase in lymphocytes (T cells and monocytes in CSF)
- slight increase in protein
- when CSF clear= aseptic meningitis
- response to pyogenic bacteria causes rapid increase in polymorphonuclear leukocytes and proteins
- CSF turbid= septic meningitis
*
- CSF turbid= septic meningitis
define bacterial meningitis and how access is gained to CNS
inflammatory bacterial infection of the meninges (mostly pia mater & arachnoid mater)
Access gained to CNS: via bloodstream after trauma or result of bacterial toxins
