Physiology & anatomy Flashcards
1
Q
Name 5 excitatory neurotransmitters and 2 inhibitory neurotransmitters
A
- Excitatory:
- Acetylcholine
- Norepinephrine
- Epinephrine
- Dopamine
- Glutamate
- Serotonin
- ATP
- Substance P
2.Inhibitory:
- GABA = gamma-aminobutyric acid
- Glycine
2
Q
What ion channels do excitatory / inhibitory neurotransmitters typically open
A
- Excitatory -> Na and K channels (depolarize membrane to ~ 0mV)
- Inhibitory -> Cl channels (hyperpolarize membrane)
3
Q
Explain excitation - contraction coupling in skeletal muscles
A
- Action potential -> depolarization of T tubules -> opening of ryanodine receptors on sarcoplasmic reticulum -> iCa release -> increase in intracellular iCa -> iCa binds to troponin C -> conformation change removing tropomyosin and allowing cross-bidging of actin and myosin
- ATP is required for myosin to be released from actin, several cycles repeat while myosin cross-bridges / releases actin and shortens the sarcomere
- SERCA channels then open and iCa is re-accumulated in the sarcoplasmic reticulum
4
Q
What are the neurotransmitters and receptors of sympathetic, parasympathetic, adrenal, and somatic nerves
A
See picture
5
Q
Where are the cell bodies of preganglionic neurons located for sympathetic and parasympathetic neurons
A
- Sympathetic: spinal cord segments T1-L3
- Parasympathetic: cranial nerves III, VII, IX, X and spinal cord segments S2-S4
6
Q
Name 1 antagonist of nicotinic receptors and 1 antagonist of muscarinic receptors
A
- Nicotinic: curares
- Muscarinic: atropine
7
Q
Name autonomic centers in the brain (and say where they are specifically)
A
- Medulla
- Vasomotor center
- Respiratory center
- Swallowing, coughing, vomiting centers - Pons
- Pneumotaxic center
- Apneustic center - Midbrain
- Micturition center - Hypothalamus
- Temperature regulation center
- Thirst center
- Food intake center
8
Q
Name the different parts of the CNS
A
- Spinal cord
- Brain stem = medulla (myencephalon), pons (metencephalon), midbrain (mesencephalon), thalamus / hypothalamus (diencephalon)
- Cerebellum (also metencephalon)
- Cerebrum (telencephalon) = cerebral cortex, basal ganglia, hippocampus, amygdala
/!\ hypothalamus and thalamus are technically part of the brainstem but functionally different ; forebrain = cerebrum + thalamus and hypothalamus
9
Q
What are the different types of glial cells and their functions
A
- Astrocytes = metabolic supply for neurons + synthesize neurotransmitters
- Oligodendrocytes = synthesize myelin in CNS (Schwann cells synthesize myelin in peripheral nervous system)
- Microglial cells = scavenger for cellular debris after neuronal injury
10
Q
Describe the sensory pathway from sensory receptor to cerebral cortex
A
- Sensory receptor ->transduce stimulus into electrical energy
- First order neuron: cell bodies in dorsal root or spinal cord ganglia
- Second order neuron: in spinal cord or brain stem (cross midline ->sensation of contra-lateral side), transmit to thalamus
- Third order neuron: in thalamus, transmit to cerebral cortex
- Fourth order neuron: in sensory area of cerebral cortex ->conscious perception
11
Q
What are the different nerve fibers and their main characteristics
A
- A-alpha -> largest and fastest fibers (sensory neurons of muscles and joints = fibers Ia and Ib)
- A-beta -> medium diameter and velocity (sensory for touch and pressure = fibers II)
- A-gamma -> medium diameter and velocity (motoneurons for muscles)
- A-delta -> small diameter, medium velocity (sensory for touch, pressure, temperature, fast pain = fibers III)
- B -> small diameter, medium velocity (preganglionic autonomic fibers)
- C -> small and slow (sensory for slow pain and temperature, postganglionic autonomic fibers = fibers IV)
12
Q
What nerve fibers are associated with nociception and what are their associated neurotransmitters
A
- Group III fibers (A-delta fibers) ->fast pain, localized
Neurotransmitter = glutamate - Group IV fibers (C fibers) -> slow pain, poorly localized
Neurotransmitter = substance P
13
Q
Name the 3 different muscle reflexes, their afferent fibers and stimulus
A
- Stretch reflex: stimulated by muscle stretch, afferent fibers Ia -> cause contraction of muscle
(patellar reflex) - Golgi tendon reflex: stimulated by muscle contraction (detected by tendon tension), afferent fibers Ib -> cause relaxation of muscle
- Flexor withdrawal reflex: stimulated by pain, afferent fibers II, III, and IV -> cause ipsilateral flexion and contralateral extension
14
Q
What motor neurons are mostly responsible for muscle contraction
A
Alpha-motoneurons
15
Q
What parts of the brain activate mechanisms for heat loss / heat gain
A
- Anterior hypothalamus -> mechanisms for heat loss
- Posterior hypothalamus -> mechanisms for heat gain
16
Q
What type of receptors are pain receptors
A
Free nerve endings
17
Q
What can excite the chemical pain receptors? What can sensitize them?
A
Bradykinin (++), serotonin, histamine, acids, ACh, potassium ions, proteolytic enzymes
Prostaglandins and substance P can sensitize them
18
Q
What are the 3 major components of the endogenous analgesia system
A
- The periaqueductal gray area and periventricular area
- The raphe magnus nucleus and nucleus reticularis paragigantocellularis
- Pain inhibitory complex in the dorsal horns of the spinal cord
19
Q
Name 2 transmitter substances involved in endogenous analgesia
A
- Enkephalin
- Serotonin
20
Q
What part of skeletal muscles is in charge of sensory function
A
Muscle spindles
21
Q
Describe the organization of cerebral blood flow
A
See picture
Carotid arteries and vertebral arteries merge to form the circle of Willis. Pial arteries rise from the circle of Willis and branch into penetrating arteries and arterioles.
Caudally, the cerebellar arteries are not part of the circle of Willis
22
Q
What regulates cerebral blood flow
A
Mostly metabolic factors: CO2, O2, H+, substances released from astrocytes
23
Q
What are the different meninges and the spaces between them
A
- Dura mater
- Arachnoid
- Pia mater
- Epidural space = outside dura mater
- Subdural space = between dura and arachnoid
- Subarachnoid space = between arachnoid and pia mater (filled with CSF)
24
Q
Where is CSF mostly produced
A
Choroid plexuses in the lateral ventricles
+ small amounts by ependymal surfaces of all ventricles and arachnoidal membranes
25
What is the composition of CFS compared to blood
- Same osmolality and Na
- Slightly more chloride than blood
- Less K and less glucose
- No proteins / cholesterol
26
Where is CSF evacuated in case of increased CSF pressure
Arachnoidal villi (flows into blood of venous sinuses)
27
What is the main integrating center of the autonomic nervous system
Hypothalamus (rostral mainly parasympathetic, caudal mainly sympathetic)
28
Explain how the synapse of a cholinergic neuron to another neuron works
- Action potential arrives at the presynaptic plate -> opens voltage-gated Ca channels -> increases intracellular iCa
- Synaptic vesicles (containing ACh) fuse with presynaptic membrane in response to iCa -> ACh released into synaptic cleft
- ACh binds receptor -> opens ligand-gated Na/K channel -> end plate potential
- ACh on receptor gets degraded by acetylcholinesterase and different parts get recycled into presynaptic neuron
29
How is ACh produced
Acetyl-CoA + choline, mediated by choline acetyltransferase
30
What are the 3 main autonomic afferent nerves? Where do they synapse?
- Facial nerve (lacrimal and salivary glands)
- Glossopharyngeal nerve (pharynx, caudal 1/3 of tongue, carotid body)
- Vagus nerve (larynx and anything caudal to it including thoracic and abdominal viscera)
They synapse in the nucleus of the solitary tract (nucleus tractus solitarius) in the medulla
31
What causes pupillary dilation / constriction
- Pupillary constriction = parasympathetic cranial nerve III
- Pupillary dilation = ocular sympathetic nerve (3-neuron system starting at hypothalamus, traveling down to T1, coming back cranially with vagosympathetic trunk, synapsing into cranial cervical ganglion, then innervating the eye)
32
What is the name of the external cerebral folds
- Outward folds = gyri
- Inward folds = sulci
33
What are the different lobes of the cerebral hemispheres (= cerebrum = telencephalon) and their main functions
- Frontal lobe = motor function
- Temporal lobe = auditory and vestibular integration
- Parietal lobe = somatosensory function
- Occipital lobe = vision
- Olfactory lobe = olfaction
34
Where is proprioception integrated
Cerebellum
35
What nerves are made of lower motor neurons
- Spinal nerves C6-T2 and L4-caudal
- Cranial nerves III-XII except VIII (not motor)
36
Where are the cell bodies of cranial nerves locates
CN I = in cerebrum
CN II = retina
CN III-IV = midbrain
CN V-VI = pons
CN VII-VIII = rostral medulla
CN IX-XII = medulla
37
Where is the Ascending Reticular Activating System (ARAS) located
Brainstem (= midbrain, pons, medulla) with projections to thalamus and cerebrum
38
What is the parasympathetic function of CN III / CN VII / CN V
- CN III: Pupil constriction
- CN VII: Lacrimation
- CN V: Salivation
39
At what level does the spinal cord terminate in dogs and cats
L6-L7 in dogs (a little more caudally for small breed dogs)
S1 in cats
In most dogs, S1-S3 innervation is at the level of L5 vertebra
40
What is the cerebral perfusion pressure
CPP = MAP - ICP
41
In what range of cerebral perfusion pressure can cerebral blood flow be maintained by auto-regulation
CPP 50-150 mmHg (or MAP 50-150 mmHg depending on the source)
42
What is the normal intracranial pressure in dogs
5-12 mmHg
43
What are the 3 homeostatic mechanism of the brain to maintain intracranial pressure stable
1. Volume buffering = displacement of CSF extracranially and decrease in cerebral blood volume when ICP increases
2. Autoregulatory mechanisms = pressure autoregulation by myogenic reflexes
(chemical autoregulation based on PaCO2 and less so on PaO2 initially surpasses pressure autoregulation with increased ICP then they both fail)
3. Cushing response = increase in MAP to maintain CPP despite increased ICP
44
What are the 3 components of the Cushing triad
- Hypertension
- Bradycardia
- Irregular respirations
45
What is the Monroe-Kellie doctrine
V intracranial = V brain + V CSF + V blood + V mass lesion
46
What are the 2 parts of intervertebral disks
- Annulus fibrosus
- Nucleus pulposus
47
Where are lower motor neuron cell bodies located
- Cranial nerve nuclei in brainstem
- Ventral horn gray matter of the spinal cord
48
What are the different types of glutamate receptors
1. Ionotropic:
- NMDA (N-methyl-D-aspartate)
- AMPA (α‐amino‐3‐hydroxy‐5‐methyl‐4‐isoxazolepro pionic acid)
2. Metabotropic: G‐protein coupled metabo tropic (mGLuR)
49
What are the 3 possible states of the neuronal voltage-gated Na+ channel
- Resting (closed)
- Open
- Inactivated (closed)
50
For each of the autonomic nervous system receptors, cite where they are located and if they have excitatory or inhibitory effects
Adrenergic receptors
- α-1 --> smooth muscle --> excitatory
- α-2 --> GI --> inhibitory/relaxation
- β-1 --> heart, SA & AV node --> excitatory
- β-2 --> smooth muscle (vascular, bronchial) --> inhibitory/relaxation
Nicotinic receptors
- Nm --> skeletal muscle --> excitatory
- Nn --> Autonomic ganglia, adrenal medulla --> excitatory
Muscarinic receptors
- M2 --> heart --> inhibitory
- M3 --> smooth muscle & glands --> inhibitory
51
For each of the autonomic nervous system receptors name agonist and antagonist drugs
See picture
52
What receptor is responsible for:
1. Pupil dilation
2. Increased renin secretion from the kidneys
3. Bladder wall relaxation
4. Bladder wall contraction
5. Bladder sphincter contraction
6. Bladder sphincter relaxation
7. Decreased heart rate and contractility
8. Increased GI motility
9. Bronchoconstriction
1. alpha-1
2. beta-1
3. beta-2
4. M3
5. alpha-1
6. M3
7. M2
8. M3
9. M3
53
What are the 3 functions of the cerebellum?
1. Vestibulocerebellum—control of balance and eye movement.
2. Pontocerebellum—planning and initiation of movement.
3. Spinocerebellum—synergy, which is control of rate, force, range, and direction of movement.
54
True or false: The composition of CSF is approximately the same as that of the interstitial fluid of the brain
True
55
What is present in larger quantities in the CSF than in the blood?
Magnesiuma and creatinine
56
Name 3 functions of the BBB
1. Maintains a constant environment for the neuron's of the CNS
2. Prevents escape of neurotransmitters
3. Protects brain from endogenous and exogenous toxins
57
What is responsible for maintaining an awake state in normal animals?
ARAS
58
At what vertebrae does the spinal cord terminate in animals?
L6-L7 in dogs
S1 in cats
59
Where do the synapses between UMN and LMN occur within the spinal cord?
Gray matter
60
Where are the LMN of clinical importance located in the spinal cord?
C6-T2 & L4-S3
61
What are the vertebral segments in the dog? Spinal cord segments?
Vertebrae:
- C1-C7
- T1-T13
- L1-L7
Spinal cord:
- C1-C8
- T1-T13
- L1-L7
- S1-S3
- Cd1-Cd5
62
Give characteristics of the following neurotransmitters (where are they produced/present, from what):
- Norepinephrine
- Epinephrine
- Dopamine
- Serotonin
- Histamine
- Glutamate
- GABA
- Glycine
- NO
Norepinephrine
- Released from postganglionic sympathetic neurons
- Bind with α or β receptors
Epinephrine
- Synthesized from norepinephrine in the adrenal medulla
Dopamine
- Prominent in the midbrain
- Released from hypothalamus
Serotonin
- Present in the brainstem
- Formed from tryptophan
- Converted to melatonin
Histamine
- Formed from histidine
- Present in the hypothalamus
Glutamate
- Most prevalent excitatory neurotransmitter in the brai
- NMDA is a glutamate receptor
GABA
- Is an inhibitory neurotransmitter.
- Is synthesized from glutamate by glutamate decarboxylase.
Glycine
- Inhibitory neurotransmitter found primarily in the spinal cord and brain stem
NO
- Short-acting inhibitory neurotransmitter in the gastrointestinal tract, blood vessels, and the central nervous system.
- Synthesized in presynaptic nerve terminals, where NO synthase converts arginine to citrulline and NO.
63
What are the 2 types of GABA receptors?
1. The GABAa receptor increases Cl− conductance and is the site of action of benzodiazepines and barbiturates.
2. The GABAb receptor increases K+ conductance.
