Neuro - Part 2 Flashcards
1
Q
What are the three parts of the brainstem?
A
- medulla, pons, midbrain
2
Q
What are some features of the medulla?
A
- crucial for life
- contains centers that regulate:
- heart rate
- blood pressure
- breathing
- waking and sleeping
- swallowing
3
Q
What are some features of the pons?
A
- influences the cortex to maintain consciousness and alertness
- influences the regulation of posture, locomotion, and visceral reflexes
- provides a pathway for the nerve fibers to relay sensory information between cerebellum and cerebral cortex
4
Q
What are some features of the midbrain?
A
- location of brainstem UMN pathways, aka extrapyramidal tracts
- subconscious posture and voluntary skilled/learned movements
5
Q
What are the different regions of the spine? Functional regions??
A
- cervical (C1-C8)
- thoracic (T1-T13)
- lumbar (L1-L7)
- sacral (S1–S3)
- caudal (Cd1-Cd5)
/
- cervical neck (C1-C5)
- thoracic limb intumescence (C6-T2)
- thorax and abdomen (T3-L3)
- pelvic cavity, pelvic limb intumescence (L4-S3)
- caudal tail (Cd-Cd5)
6
Q
What is the structure of the spinal cord?
A
- transversely tubular, with a small central canal with CSF, anatomically divided into peripheral white matter and central grey matter
7
Q
What are some features of grey matter in the spinal cord?
A
- integrative area for cord reflexes**
- sensory signals enter almost entirely from the sensory roots (dorsal horn)
- after entering the cord, each signal travels to different locations
- one branch terminates in grey matter and elicits local reflexes
- another branch transmits signals to higher levels of the ns (cord/brainstem/cerebral cortex)
8
Q
What are the components of the PNS?
A
- composed of all neural tissue outside the CNS
- receptors, nerves, and peripheral ganglia
- connect CNS to limbs/organs
- delivery sensory info to CNS
- carry motor info to peripheral tissues/systems
9
Q
What are the kinds of sensory neurons (afferent)?
A
- Primary/First-Order Neurons (PNS)
- receive signal + send info to CNS
- Secondary/Second-Order Neurons (CNS)
- send impulses from spinal cord/brainstem to thalamus, switches sides (ex: L to R)
- Tertiary/Third-Order Neurons (CNS)
- conduct impulses from thalamus to primary somatosensory cortex
- Quaternary/Forth-Order Neurons (CNS)
- located in sensory area of the cerebral cortex
10
Q
What are the kinds of motor nerves (efferent)?
A
- upper motor nerve (UMN)
- completely contained in CNS
- lower motor nerve
- cell body in CNS, axons in PNS
- ** except for post-ganglionic autonomic motor neuron
- completely in PNS
11
Q
What are ganglia?
A
- bunch of nerve bodies outside the CNS
12
Q
What is the organization of nerve fibers?
A
- just like muscle fibers!
- nerve fiber (axon + myelin sheath) < endoneurium (CT) < fascicle < perineurium (CT) < peripheral nerve < epineurium (CT)
13
Q
What are the three main components of a spinal nerve?
A
- roots (dorsal + ventral)
- main trunk
- peripheral branches
14
Q
What are some features of spinal nerves?
A
- communicate w/ spinal cord via sensory receptors, muscles, viscera, and vessels
- exit the vertebral canal via lateral cerebral foramen of the atlas or via intervertebral foramen
- each segment of the spinal cord is paired to special nerves (7C, 13T, 7L, 3S, 10-24Cd)
- neurons innervating the limbs (LMNs) are confined to the cervical + lumbar intumescences
- cranial part innervates cranial + proximal muscles of the limb
- caudal part innervates distal + caudal muscles of the limb
15
Q
T/F: A peripheral ganglion is located distally to each ventral horn
A
- False; dorsal root
16
Q
What are the 4 types of fibers present in all spinal nerves?
A
- somatic sensory neurons
- enter the cord through the dorsal root
- visceral sensory neurons
- ener the cord through the dorsal root
- somatic motor neurons
- exit the cord through the ventral root
- visceral motor neurons
- exit the cord through the ventral root
17
Q
After leaving the intervertebral foramen, the main trunk gives off a __________ and ___________ branch, which connects the ____________________ with the spinal nerve.
A
- dorsal + communicating
- sympathetic trunk ganglion of the sympathetic chain
18
Q
What are some features of cranial nerves?
A
- 12 pairs innervate the head and extend into the body
- most arrive in brainstem
- individual nerves have specific sensory and/or motor, somatic, or autonomic functions
19
Q
What are the three meninges?
A
- dura mater, arachnoid, pia mater
20
Q
What are characteristics of dura mater?
A
- “hard mother”
- outermost meningeal layer
- often fused with inner surface of skull
- thicker, protects CNS
21
Q
What are characteristics of arachnoid?
A
- “web form”
- spider web appearance, extensive network of trabeculae that join pia mater
- thin, loose, connective tissue layer
- subarachnoid space between arachnoid and pia matter that traps CSF to be absorbed
22
Q
What are characteristics of pia mater?
A
- “soft mother”
- innermost meningeal layer
- adheres to surface of CNS
23
Q
What are some features of blood supply for the CNS?
A
- CNS is 2% of body weight, but receives 20% of cardiac output due to high metabolic rate
- oxygen requirements for synapses and cell bodies are greater than for axons, grey matter gets more blood than white matter
- association/integration areas have higher requirements than other areas (ex: forebrain is more vascular)
- CNS and meninges drained by veins and sinuses
24
Q
What are the regions of the ventricular system?
A
- lateral ventricles (2): oriented longitudinally in each hemisphere, connected to the 3rd
- third ventricle: surrounding the interthalamic adhesion and connected to the 4th
- fourth ventricle: connected with the subarachnoid space and central canal of spinal cord
25
Q
Where is CSF stored?
A
- subarachnoid space, ventricular system, central canal through core of spinal cord
26
Q
What are some functions of CSF?
A
- clear fluid w/ several functions:
- protect brain/spinal cords against impact w/ surrounding bone
- effective waste control system that can remove potentially harmful cellular metabolites
- act as brain distribution system for some peptide hormones/growth factors
- maintain a consistent extracellular micro environment for neurons and glia
- protect brain/spinal cords against impact w/ surrounding bone
27
Q
How do neurons and neuroglia recieve essential materials?
A
- capillaries in choroid plexus: provide micronutrients
- interstitial capillaries: provide O2 + substances consumed in large amounts
28
Q
Where is CSF produced?
A
- mostly the choroid plexus of the ventricles:
-cauliflower like growth of capillaries covered by a thin layer of modified ependymal cells - ependymal lining of ventricles
- glial limiting membrane between brain/spinal cord and pia mater
29
Q
What kind of junction is found in epithelial cells?
A
- tight junctions
- seal gap between epithelial cells
- seal intercellular space from luminal environment
- not absolute: impermeable to macromolecules, permeable to ions and some other small molecules
- most apical location
- found in epithelial cells (ex: lining interstitial mucosa, bladder etc.)
30
Q
How many times does CSF replace in a day? What are some features of this?
A
- rate of formation, flow, and absorption allows for replacement ~ 4 times/day
- formation is fairly constant and independent of changes in pressure
- most of the CSF is absorbed from the subarachnoid space into the venous sinuses through arachnoid villi; small finger-like projections of the arachnoid membrane that poke through the dura mater in the lumen of various sinuses
31
Q
Why does the choroid epithelium form a selective tight-junction barrier?
A
- to control the composition of CSF that enters the ventricles
- created from blood plasma
- 99% water, other %’s of ions, almost NO proteins , micronutrients
32
Q
What is the pathway of CSF secretion?
A
- water in choroid epithelial cells combines w/ intracellular CO2 produced by cell metabolism to form H+ and HCO3-
- at the basal surface, H+ is exchanged for extracellular Na+ from blood
- influx of Na+ results in excess positive charge
- to neutralize this Cl- and HCO3- move into ventricles
- Na+ is pumped out through apical surface into the ventricles
- water also diffuses into the ventricles to maintain osmotic balance
33
Q
Absorption of CSF is _________ and __________
A
- pressure dependent + unidirectional
- from subarachnoid space to venous outflow system
34
Q
Where is the blood brain barrier and blood-CSF barrier located?
A
- barriers located at both the choroid plexus and at tissue capillary membranes in all areas of brain
- exception some areas like hypothalamus and pituitary gland that have sensory receptors that respond to changes in body fluid like osmolity or glucose concentration
35
Q
What causes the blood brain barrier to be low permeability?
A
- the manner in which the cells are joined to one another, via tight junctions
- astrocytes form a perivascular end foot around the entire outer surface of the capillary end; the interactions between the astrocytes + endothelial cells are important for bbb maintenance
36
Q
What is the permeability of the BBB?
A
- highly permeable to water, CO2, O2, and most lipid-soluble substances (ex: alcohol + anesthetic)
- slightly permeable to plasma proteins, and non-lipid-soluble large organic molecules
37
Q
How does the brain receive certain nutrients that are restricted by the BBB?
A
- glucose: uses GLUT 1 and facilitated diffusion
- large neutral amino acids: some are precursors for neurotransmitters, use facilitated diffusion
- small neutral amino acids: synthesized in the CNS
38
Q
What do dendrites do? Axons?
A
- integrate incoming information and determine whether action potentials will be produced by the neuron
- ability to transport cargo either direction via cytoskeleton and different proteins
39
Q
What are the kinds of synapses?
A
- chemical
- MOST COMMON, usually unidirectional transmission; presynaptic neuron secretes a neurotransmitter that will act on receptor proteins in the postsynaptic neuron (excitatory or inhibitory)
- electrical
- cytoplasm of adjacent cells is directly connected by clusters of ion channels called gap junctions, bidirectional transmission, coexist and interact with chemical synapses, promote synchronous firing of interconnected neurons
40
Q
What are the two kinds of neurotransmitters?
A
- conventional: share basic features; stored in vesicles, released when Ca2 enters axon in response to AP, act by binding to receptors on membrane of postsynaptic cell (small + large molecule neurotransmitters)
- unconventional: several classes that dont follow usual rules; not stored in vesicles, can carry signals backwards, not dependent on receptors (ex: endocannabinoids, gasotransmitters)
41
Q
What are types of synapse interfaces?
A
42
Q
Differentiate between ionotropic and metabotropic receptor proteins
A
- ionotropic
- neurotransmitter receptor that directly gates ion channels:
- cation channels - opened by excitatory neurotransmitters, induce depolarization (ex: Na+ channels)
- anion channels - opened by inhibitory neurotransmitters, induce hyperpolarization (ex: Cl- channels)
- neurotransmitter receptor that directly gates ion channels:
- metabotropic
- neurotransmitter receptor that act through second messenger systems
- G-protein coupled receptors - open specific ion channels in postsynaptic membrane, activate cAMP, activate intracellular enzymes, activate gene transcription
- neurotransmitter receptor that act through second messenger systems
43
Q
How are graded potentials initiated?
A
- a neuron receives hundreds of inputs from other neurons in response to neurotransmitters from presynaptic neurons
- brief local changes in post-synaptic membranes are generated (graded potentials)
44
Q
The amplitude of graded potentials is __________________ to the intensity of the stimulus applied at synaptic sites
A
- directly proportional
- each synaptic site generates graded potentials, thousands of graded potentials occur at cell bodies and dendrites and travel to reach the axon hillock/trigger zone
45
Q
What is the trigger zone?
A
- axon hillock
- where graded potentials are integrated to generate action potentials, this zone is more sensitive to the depolarizing action of local currents
- in order to initiate an action potential, graded potentials must reach a certain level: threshold potential/threshold voltage (-55 mV)
- once the sum of graded potentials exceeds the threshold, an action potential will be triggered. AP propagates along axon. **if depolarization does not reach threshold, no AP will occur, then graded potentials decay.
46
Q
Graded potentials modulate the postsynaptic neuron by shifting the resting membrane potential, through _______ and ________
A
- excitatory postsynaptic potentials EPSP (shift TOWARDS threshold potential)
- depolarization (shift MP toward more +), excitatory neurotransmitters open cation channels, ex: glutamate
- inhibitory postsynaptic potentials IPSP (shift AWAY FROM threshold potential)
- hyperpolarization (shift MP toward more -), inhibitory neurotransmitters open anion channels, ex: GABA
47
Q
What are the two modes of summation?
A
- spatial summation
- graded potentials induced by different synapses summate in the postsynaptic neuron, SIMULTANEOUS summation of IPSP & EPSP graded potentials also occur
- temporal summation
- successive discharges from a single presynaptic terminal summate in the PS neuron if they are rapid enough
48
Q
What is saltatory conduction?
A
- all AP generated at the trigger zone are identical and propagate without losing strength
- AP occur only at nodes of ranvier in myelinated fibers, “jump” aka REGENERATE from node to node, electrical current flows through axoplasm inside the axon
