Midterm Flashcards
What are the categories of protein function?
- catalysis
- Reaction coupling
- Transport
- Structure
- Signaling
What is the ability to increase the rate of a chemical reaction without altering the equilibrium of the reaction?
catalysis
What is two reactions joined together with the transfer of energy?
Reaction coupling
What are the common mechanisms that result in allosteric shape change?
- ligand binding
- phosphorylation
- voltage-dependent proteins
The binding of one ligand changes the binding site shape of another ligand
Ligand binding
Adding a phosphate group to certain amino acids on the protein
phosphorylation
The electrical field surrounding some proteins can change the conformation of some proteins
voltage-dependent proteins
Molecules that can readily pass through membrane
small, uncharged molecules and lipid-soluble molecules
Molecules that cannot readily pass through membrane
ions, large polar molecules
Factors that determine the driving force of molecules across cell membranes
- chemical concentration
- electrical gradient
- pressure
Determined by the differences in the number of molecules in and out of cells
chemical concentration
Difference in electrical charges across the cell membrane
electrical gradient
spontaneous net movement of solvent molecules through a selectively permeable membrane into a region of higher solute concentration
osmosis
Osmotic pressure resulting from dissolved blood proteins
colloidal pressure or oncotic pressure
Couples movement down an electrochemical gradient to the uphill movement of another molecule against a electrochemical gradient
secondary active transport
Methods of facilitated diffusion
- ungated channel proteins
- carrier proteins
- Ligand-gated channel
- voltage-gated channel
Any abnormality in a tissue/organ
lesion
The reaction of living tissue to local injury
inflammation
5 cardinal signs of inflammation
- heat
- redness
- swelling
- pain
- loss of function
What normal tissues look like under a microscope
histology
What abnormal tissues look like under a microscope
histopathology
Spherical mass of cells
morula
the cells that end up on the outside and give rise to the epithelial layer
trophoblast
cells on the inside
inner cell mass
The layer of trophoblasts and the outer cells of the inner cell mass fuse to become the embryonic disc
epiblasts
inner cells of the inner cell mass
hypoblasts
What becomes ectoderm and mesoderm
cells from the embryonic disc
What becomes endoderm
hypoblasts
Stage where the three primary germ layers are formed
gastrulation
What does ectoderm become?
skin and associated glands, neuroectoderm
What does mesoderm become?
supportive tissues, circulatory system, urogenital
What does endoderm become?
lining of GI system, lining of respiratory system, lining of urinary bladder, liver, pancreas
Mass/swelling/nodule
tumor
New growth. Mutated cells allow for uncontrolled cell growth
neoplasia
benign tumors of epithelial cells
adenomas
benign tumor of mesenchymal cells
fibroma
Malignant tumor from epithelial cells
carcinoma
malignant tumor from mesenchymal cells
sarcoma
Midline indentation on the surface of the embryonic disc
primitive streak
Extends along the midline of the length of the embryo. Becomes IV discs
notochord
Ectoderm above the notochord. Invaginates to form the neural groove
Neuroectoderm
Failure of complete closure of the neural tube
spina bifida
Neuroectodermal cells that migrate laterally
neural crest cells
What do neural crest cells become?
melanocytes, Schwann cells, adrenal medulla cells, some nerve cells, autonomic ganglion
Failure of migration of neural crest cells
lethal white foal syndrome
Directly surrounds the embryo. Mechanical protection. Is lined by ectoderm and is continuous with the skin of the baby
amnion
outermost membrane the interdigitates with the lining of the uterus for the exchange of nutrients and waste
chorion
Cranial outpouching of fetal gut
yolk sac
Caudal outpouching of fetal gut
allantois
Common passageway for the intestinal and urinary tracts
cloaca
Urachus does not pinch off and close at birth. Urine leaks out, causes UTI
patent urachus
How does digestive system form?
begins as a tube of endoderm that runs the length of the embryo
When abdominal wall doesn’t close
umbilical hernia
Umbilical hernia complications
intestines get stuck through hole, lose their blood supply, intestinal bacteria enter bloodstream
Failure of the anal membrane to break down
atresia ani
How do liver and pancreas develop?
outgrowth of the proximal duodenum
Key functional element of an organ
parenchyma
Supportive framework
stroma
How do lungs develop?
outgrowth of the embryonic gut tube
How does urinary system develop
- ureteric buds arise from the urachus to become ureters
2. Ureteric buds induce formation of the metanephros from the adjacent mesoderm
Formation of cardiovascular system
- mesoderm aggregates into blood islands
- cells on the periphery flatten out to become squamous cells
- cells in the center become blood precursors
- This creates a series of paired tubes
- Fuse with each other
- Folding to make heart
Failure of complete division of the ventricles
ventricular septal defect
How fetal blood bypasses the liver and enters the caudal vena cava
ductus venosus
What the ductus venosus becomes
ligamentum venosum
How fetal blood from the caudal vena cava enters the right atrium and bypasses the lungs
foramen ovale
What does the foramen ovale become?
fossa ovalis
How fetal blood bypasses the lungs by going into the aorta
ductus arteriosis
What does the ductus arteriosis become?
ligamentum arteriosum
What part of mesoderm adjacent to the neurotube becomes skeletal muscle?
myotome
What part of mesoderm adjacent to the neurotube becomes dermis?
dermatome
What part of mesoderm adjacent to the neurotube becomes cartilage and bone?
sclerotome
What is the central NS derived from?
neuroectoderm
What is the peripheral NS derived from?
neural crest cells
Parts of a neuron
- dendrites
- nucleus
- axon
- cell body
- axon terminals
Receive signals from other tissues or nerves and relay them to the nucleus for processing
dendrites
signals head away from the nucleus on their way to other nerves or effector tissues
axons
Signal is passed to another neuron at synapse
axon terminal
Cells that surround and support neurons
neuroglia
Most numerous neuroglial cells in gray matter
atrocytes
parts of brain with a high density of neuronal cell bodies
gray matter
Where there are clusters of axons
white matter
Mesenchymal cells that have an immune function and are considered part of the macrophage-monocyte defense system
microglia
Cuboidal cells that line the ventricles of the brain and spinal canal
ependymal cells
most numerous neuroglial cell in white matter. Surround axons and form myelin
oligodendrocytes
Oligodendrocyte in peripheral NS
Schwann cell
Gaps between Schwann Cells
Nodes of Ranvier
Makes CSF
choroid plexus
Failure of reabsorption of CSF
hydrocephalus
Connective tissue layers that surround the central NS
Meninges
functions of meninges
- Provide support for the blood vessels that feed the brain and spinal cord
- keep the CSF close to the brain and spinal cord
- tether the brain and spinal cord to the overlying bone
Layers of meninges
- pia mater
- arachnoid mater
- dura mater
Thinnest layer of meninges
pia mater
Thickest layer of meninges, fused to the inside of the skull
dura mater
Cranial 2/3 of brain
cerebrum
where is gray and white matter in cerebrum
white matter inside, gray matter outside
Caudal 1/3 of the brain, tree of life
cerebellum
Layers of cerebellum
- molecular layer
- Purkinje cell layer
- Granular cell layer
Gray and white matter in spinal cord
gray matter inside, white matter outside
Collection of neurons on the PNS
ganglia
Collections of axons in the PNS
nerves
Collections of axons in the CNS
tracts
Sensory division of the Peripheral NS
afferent
motor division of PNS
efferent
From skin, retina, and membranous labyrinth
somatic afferent system
Somatic Afferent System
from skin, retina, and membranous labyrinth
from thoracic and abdominal organs, olfactory epithelium, and taste buds
visceral afferent system
Visceral Afferent System
from thoracic and abdominal organs, olfactory epithelium, and taste buds
to skeletal muscle, responsible for voluntary control
somatic efferent system
Somatic Efferent System
to skeletal muscle, responsible for voluntary control
to cardiac muscle, smooth muscle, and glands
visceral efferent system
Visceral Efferent System
to cardiac muscle, smooth muscle, and glands
Information flow in a neuron
- dendrites
- soma
- axon
- pre-synaptic terminal
Contents of the soma
nucleus, ribosomes, rER, golgi
Charge inside a neuron
negative
How is charge inside a neuron maintained
by Na K pump
More positive than resting membrane potential, inward flow of positive charge
Depolarized
More negative than resting membrane potential, outward flow of positive charge
Hyperpolarized
Post-synaptic potential that is more positive, closer to reaching action potential
excitatory post-synaptic potential. Influx of Na
Post-synaptic potential that is more negative, less likely for an action potential
inhibitory post-synaptic potential. Cl influx of K efflux
Summation from multiple dendrites
spatial summation
summation from same dendrite
temporal summation
Why do we need summation
because a single discharge of presynaptic terminal onto dendrite does not initiate action potential
Characteristics of an action potential
- fixed in amplitude
- uniform shape
- begins at an axon’s initial segment
- not graded
- rapidly spreads down axon
Stages of an action potential
- resting stage
- depolarization stage
- repolarization stage
Stage of an action potential where cell is polarized (negative inside cell)
resting stage
Stage of an action potential where depolarization above threshold triggers all or nothing response. Opening of voltage gated Na channels
depolarization stage
Stage of an action potential where Na channels close and voltage-gated K channels open. Rapid diffusion of K out of cell
repolarization stage
Depolarization Stage
depolarization above threshold triggers all or nothing response. Opening of voltage gated Na channels
Repolarization Stage
Na channels close and voltage-gated K channels open. Rapid diffusion of K out of cell
Characteristics of axonal conduction
axons carry electrical signals rapidly, efficiently, and reliably
How to increase conduction speed
larger diameter, myelination
Types of synapses
electrical and chemical
Type of synapse in the CNS and NMJ
chemical synapse
Type of synapse that is at smooth and cardiac muscle with gap junctions that allow free movement of ions
electrical synapse
Process of Transmission
- NT packaged into synaptic vesicles
- AP arrives at pre-synaptic terminal
- opening of voltage gated Ca channels
- Fusion of vesicles with membrane and release of NT
- NT diffuses across synapse and binds receptor
- Activation of postsynaptic cell
Neurotransmitter release
- presynaptic membrane contains voltage gated Ca channels
- AP at presynaptic terminal causes Ca channels to open
- Ca facilitates fusion of synaptic vesicles with membrane
- NT binds to receptor on postsynaptic cell
Consequences of NT binding
excitation or inhibition
Excitation
opening of Na channels. Decreased diffusion of Cl into cell or K out of cell. Changes in internal metabolism
Inhibition
opening of Cl channels. Increased diffusion of K out of cell. Enzymes that inhibit cellular metabolism
What is the excitatory neurotransmitter at the NMJ?
acetylcholine
Structure of Post synaptic membrane at NMJ
junctional folds or subneural clefts. Increase surface area
Breakdown of acetylcholine
- in the synapse acetylcholine is rapidly broken down by acetylcholinesterase
- Choline is transported back into the axon terminal and used to make more acertylcholine
Consequence at Nerve-Nerve Junction
- may be excitatory or inhibitory
- uses a variety of neurotransmitters
- can be bi-directional transmission
- Variety of receptor types
- AP often have to summate for post-synaptic AP
- Relies on Ca influx for neurotransmitter release
Consequences at NMJ
- NMJ produces excitation
- uses acetylcholine
- one-way transmission
- Nicotinic receptor
- AP leads to muscle contraction
- Relies on Ca influx for neurotransmitter release
What is the only similarity between nerve-nerve and NMJ?
relies on Ca influx for neurotransmitter release
Ultrafiltration of blood plasma modified by active transport
Cerebrospinal fluid
Rate of production of CSF
constant
Direction of CSF Flow
cranial-caudal
Circulation of CSF
- lateral ventricles
- 3rd ventricle
- cerebral aqeuduct
- 4th ventricle
- subarachnoid space via lateral apertures
What determines the rate of CSF flow
the pulsation of blood in the choroid plexus
Where is CSF absorbed?
arachnoid villi
Fingerlike inward projections of arachnoid membrane
arachnoid villi
Functions of CSF
- physical protection
- chemical buffer
- pressure regulation
- source of nourishment/waste removal
Selective barrier between systemic circulation and the central nervous system
blood brain barrier
Components of the BBB
- nonfenestrated tight junctions of endothelial cells of the capillary wall
- Endothelial cells surrounded by thick basement membrane
- Layer of foot processes from astrocytes on the surface of the basement membrane
Highly permeable to BBB
water, CO2, O2, and most lipid soluble substances
Slightly permeable to BBB
electrolytes
Impermeable to BBB
plasma proteins, most non-lipid soluble, large organic molecules
Areas that lack a BBB
circumventricular organs- hypothalamus, area postrema, pineal gland
Coordinate autonomic nervous system with pituitary, sleep, and emotional activity
hypothalamus
in medulla oblongata, control vomiting
area postrema
Function not completely understood, regulates some hormones
pineal gland
Connective tissue is derived from which embryonic layer?
mesoderm
Functions of connective tissue
- structural support
- metabolic support
- thermoregulation
- immune defense
- tissue repair
Main types of connective tissue
- connective tissue proper
- embryonic connective tissue
- special types
Most common cell type in connective tissue. Spindle shaped with elongate nuclei and scant cytoplasm
fibroblast
Activated and modified fibroblasts that have contractile activity
myofibroblast
Cell types in connective tissue
- fibroblasts
- myofibroblasts
- adipocytes
- immune cells
Most common fiber in connective tissue, stains pink with routine stains
collagen
Function of collagen
provide tensile strength
Provides for stretch and recoil. Looks like collagen with routine stains
elastin
Link proteins in the cell membranes to the extracellular matrix
structural glycoproteins
Important structural glycoprotein
fibronectin
Semi-fluid gel that contains glycosaminoglycans
ground substance
Predominant glycosaminoglycan in ground substance
hyaluronic acid
Attract water to keep the fluidity of the ground substance
Glycosaminoglycans
Glycosaminoglycans associated with proteins
proteoglycans
Types of Connective Tissue Proper
- regular
- irregular
- reticular
- elastic
- adipose
Type of connective tissue where forces are in one direction. Closely packed, parallel bundles of collagen
Regular connective tissue proper
Where is regular connective tissue proper found?
tendons and ligaments
Type of connective tissue where forces are applied in multiple directions and collagen fibers course in all directions
Irregular connective tissue proper
Types of irregular connective tissue proper
loose and dense
More ground substance than fibers
loose irregular connective tissue proper
Where is loose irregular connective tissue proper found?
surrounding vessels and nerves, forms the mesentery
More fibers than ground substance
dense irregular connective tissue proper
Where is dense irregular connective tissue proper found?
deep layers of the skin, submucosa of intestines, organ capsules
Type of connective tissue where main fiber type is reticulin. Looks pink with routine stains. Form a branched network that support the cells in parenchymal organs
reticular connective tissue proper
Where is reticular connective tissue found?
spleen, lymph node, liver, kidney, bone marrow
predominate fiber type is elastin. Elastin is technically not a type of collagen. Can’t see elastin well with routine stains. Provides flexibility to tissues.
Elastic connective tissue
Where is elastic connective tissue found?
blood vessels, external ear, vocal chords, trachea, lung, skin
white fat
White Adipose Tissue
Functions of White Adipose Tissue
- energy storage
- shock absorption
- insulation/thermoregulation
Where is white adipose tissue found?
- within and around muscle
- subcutaneous
- falciform ligament
- mesentery
- around the kidneys
signet-ring shaped. Large central lipid droplet which compresses and peripheralizes the nucleus.
shape of white adipose cells
Function in thermoregulation (mitochondria produce heat instead of ATP). Cells contain multiple small lipid droplets and lots of mitochondria. The nuclei are plump and round. Lipid droplets will vary in size, even within a cell and within a group of brown fat cells. Found in neonates, rodents, and hibernating animals.
brown adipose tissue
Muscle functions
- voluntary control (locomotion, controlling bodily functions)
- involuntary control (heart beating, dilation or constriction of arteries, peristalsis in digestive tract, parturition)
Cell membrane of myofibers
sarcolemma
cytoplasm of myofibers
sarcoplasm
contains myofilaments which are anchored to the cell membrane. Actin (thin), myosin (thick), which are connected together and movement of them against each other pulls the cell membrane to move the cell.
sarcoplasm
Shape of Nucleus of myofibers
oval
Muscle is derived from which embryonic layer?
mesoderm
Types of muscle
smooth, skeletal, cardiac
Where is smooth muscle found?
digestive tract, blood vessels, urinary bladder, bronchi and bronchioles, iris, piloerecti muscles
Increase in the size of cells
hypertrophy
Decrease in the size of cells
Atrophy
Reflex Arc Components
- sensory receptor
- sensory neuron
- synapse
- motor neuron
- target organ
connection between incoming sensory neuron and 2nd neuron
syanpse
translates stimulus into action potential. Ex: muscle stretch, pain, light
sensory receptor
carries action potential from receptor to CNS
sensory neuron
carries action potential from CNS to effector organ
motor neuron
goes into nervous system and comes out at same level. Only involving small segment of CNS
segmental reflex
Goes in one area, travel far back in nervous system, and then back out
intersegmental reflex
sense of where your body is in space
Proprioception
partial loss of voluntary motor function. The P has loss of strength but still some voluntary movement
Paresis
P is weak but still able to walk
ambulatory paresis
P has feeble voluntary movement but is not strong enough to walk on their own
Nonambulatory paresis
wants to contract muscle, sends AP to lower motor neuron what to do
upper motor neuron
Where is the LMN Located?
gray matter of spinal cord for limbs
Resistance to muscle stretch
muscle tone
Total loss of voluntary movment
paralysis
Will a paralyzed patient still have spinal cord reflexes?
yes because spinal cord reflexes are not voluntary
one limb is involved
mono
both pelvic limbs
para
all four limbs are affected
tetra
Segments of the spinal cord
8 cervical 13 thoracic 7 lumbar 3 sacral 5 caudal
Cervical spinal cord
C1-C8
Thoracic Spinal cord
T1-T13
Lumbar spinal cord
L1-L7
Regions of the spinal cord that innervate all the muscles of the limbs and therefore contain many more LMN cell bodies and are larger in diameter
Intumescences
Where are the LMN for thoracic limbs?
C6-T2
Where are the LMN for the pelvic limbs
L4-S3
Where are the cell bodies for the UMN?
the brain
Where are the axons for the UMN for the thoracic and pelvic limbs?
C1-C5
Where are the axons for the UMN for pelvic limbs?
T3-L3
Signs of a LMN Lesion
- paresis or paralysis
- weak to absent reflexes
- weak to absent muscle tone
- rapid, severe muscle atrophy
Signs of an UMN lesion
- paresis or paralysis
- normal to exaggerated reflexes
- normal to increased muscle tone
- only mild muscle atrophy
withdrawal reflex in one limb causes the other limb to extend while recumbent
crossed extensor reflex
alternating extension and flexion of the stifle in response to a single tap of the patellar tendon
clonus of patellar reflex
increased muscle tone. Characterized by increased tone in the extensor muscles such that the patient does not flex the limb normally during the protraction phase of the gait (when the limb is moving forward), resulting in a stiff stilted gait
Spasticity
What does a focal spinal cord lesion cause?
- lower motor neuron deficits at the level of the lesion
- Upper motor neuron deficits caudal to the lesion
- sensory deficits at the level of and caudal to the lesion
Forebrain/brainstem lesion
tetraparesis/tetraplegia with normal to increased reflexes and muscle tone in all limbs
C1-C5 Lesion
tetraparesis/tetraplegia with normal to increased reflexes and muscle tone in all limbs
C5-T2 Lesion
tetraparesis/tetraplegia with weak to abesnt reflexes and decreased muscle tone in the thoracic limbs and normal to increased reflexes and muscle tone in the pelvic limbs
T3-L3 Lesion
Paraperesis/paraplegia with normal to increased reflexes and muscle tone in the pelvic limbs
L4-S3 Lesion
paraparesis/paraplegia with decreased to absent reflexes and muscle tone in pelvic limbs
Diffuse LMN Lesion
tetraparesis/tetraplegia with weak to absent reflexes and muscle tone in all limbs
Reflexes generate alternating stepping movements in legs. In severe UMN lesion, you have a reflex stepping movement where pelvic limbs are spastic
Spinal Walking
Upper Motor Neuron Systems
- corticospinal
- Rubrospinal
- vestibulospinal
- reticulospinal
diffuse groups of neuronal cell bodies in the brainstem
Reticular Formation
. From reticular formation to spinal cord. synapse on lower motor neurons in spinal cord. Maintain posture and muscle tone
Reticulospinal neuron system
middle portion of brainstem. Facilitates flexion
pons
Back portion of brainstem, facilitate extension
medulla
Lesion in brain causes functional disruption in front of brain stem. Neurons in pons cannot facilitate flexion.
Decerebrate Posture
from vestibular neurons to spinal cord. Vestibular nuclei are in the brainstem. LMN in spinal cord responsible for antigravity muscles
Vestibulospinal Neuron System
From red nucleus in midbrain (front portion of brainstem). Input on more distal limb muscles for control of finer movement. Most important in nonprimates
Rubrospinal neuron systemq
Which system is most important to nonprimates
rubrospinal
from cerebral cortex to spinal cord. Motor cortex in cerebrum. Descending tract decussates. Spinal LMN involved in voluntary movement. Most important in primates. Lesion in this pathway causes total paralysis in primates. Only weakness in non-primates
Corticospinal
Which system is most important in primates
Corticospinal
What is the other name for the corticospinal tract
pyramidal tract
corticospinal and corticobulbar
pyramidal tracts
Reticulospinal, vestibulospinal, and rubrospinal
extrapyramidal tracts
Functions of the Vestibular System
- Maintain upright posture
2. coordinate head movement with eye movement
Parts of the inner ear
cochlea (hearing), utricle and saccule (linear acceleration/gravity), 3 semicircular canals (rotary acceleration)
Hair Cells
movement of cilia converted into action potentials. Tonically active: bend one way increases activity, bend the other way decreases activity
Semicircular canals
superior semicircular canal, lateral semicircular canal, and posterior semicircular canal. They are oriented in different planes- one vertical, one horizontal, and one back and forth
detect tilt, gravity. And detect linear acceleration
Utricle and saccule
Head Tilt
towards the lesion of a peripheral vestibular lesion
Rotation Induced Eye Movement
eyes move in an equal and opposite direction (slow phase). Forebrain induces corrective movement toward direction (fast phase)
Lesion Eye Movement
eyes move toward lesion (slow phase). Corrective phase away from lesion (fast phase)
horizontal nystagmus, fast phase to the right. Left peripheral vestibular lesion
Spontaneous Nystagmus
equal speed in each direction. Congenital abnormality in the visual pathways. Not a vestibular lesion
Pendular Nystagmus
Cerebellar lesion head tilt
away from lesion
What can vestibular lesions cause?
head tilt, leaning and falling (vestibular ataxia), abnormal eye movements
What is another name for the autonomic nervous system?
visceral efferent system
What are the two branches of the autonomic nervous system?
sympathetic and parasympathetic
Autonomic Nervous System Characteristics
independent. Composed of efferent fibers forming a reflex pathway responding to visceral afferents.
What are the actions of the ANS controlled by?
hypothalamus and reticular formation
conserves and restores energy (rest and digest)
parasympathetic NS
prepared the body for emergency situations (fight or flight)
sympathetic NS
SNS and PNS activity
parasympathetic is continuously active
Sympathetic has low resting tone but is capable of bouts of great activity
Anatomy of the ANS
is a 2 neuron system.
1. 1st neuron in cell body
2 . 2nd neuron on ganglion in the peripheral NS
Where do preganglionic ANS nerve fibers leave the CNS?
parasympathetic= craniosacral nervous system Sympathetic= thoracolumbar nervous system
Anatomy of the Preganglionic Cell Bodies
all pre-ganglionic cell bodies are in the lateral horn of T1-L3. Short axons run to sympathetic trunk ganglia. Form the sympathetic trunk
some individual ganglion have fused together. Head supplied by spinal nerves from C8-T5. Part of the vagosympathetic trunk
Sympathetic trunk
Targets of sympathetic nervous system
- dilate pupil
- constrict blood vessels in skin and gut
- bronchodilation
- increase heart rate and force of contraction
- piloerection
- decrease peristaltic activity and secretion in gut
- stimulation of secretion from sweat glands
- stimulate release of norepinephrine and epinephrine from adrenal medulla
- close the internal urethral sphincter
Target Organs of Parasympathetic Fibers
pupil size via CN III (oculomotor nerve)
salivary glands via CN VII (facial n.) and IX (glossopharyngeal n.)
Lacrimal glands via CN VII (facial nerve)
vagus nerve. Projects to parasympathetic ganglia in or close to thoracic and abdominal organs- in cardiac muscles to regulate heart rte, gastrointestinal tract to regulate motility and secretions, and lungs to regulate secretion
Cranial Nerve X
Where do sacral preganglionic neurons exit the CNS?
via spinal nerves (S1-S3) and form the pelvic nerces to end in the pelvic viscera (rectum, bladder, genitalia)
Target Organs of the Parasympathetic Fibers
- constriction of pupil
- accomodation of the lens
- bronchoconstriction
- decrease heart rate
- increase peristaltic activity and secretion in gut
- release of saliva
- contracts the bladder
- stimulates erection
molecule released by a neuron at the level of the synapse following an action potential. Acts as a chemical messenger, binds to post-synaptic receptors, generates a change in function of the target cell
Neurotransmitter
innervated by sympathetic fibers. Preganglionic neuron secreted acetylcholine. Postganglionic chromaffin cells acting like 2nd neurons secrete epinephrine (and a small amount of norepinephrine). The epinephrine is released in the blood circulation allowing diffuse systemic effects following sympathetic stimulation
adrenal medulla
receptors to pressure, stretch, and chemical changes
General visceral afferent system
receptors to taste and olfaction
specific visceral afferent system
What only receives sympathetic innervation?
vessles
Functions of the Sympathetic Nervous System
- response to an emergency situation
- response to physical or emotional stress
- secretion of epinephrine by adrenal glands prolongs the effect
- digestion and urination are inhibited
- helps with thermoregulation and allows pupils to dilate in low ambient light in less stressful situations
Functions of the Parasympathetic Nervous System
- digestion and food absorption
- pupillary constriction
- decreases heart rate
- urination
- defecation
- lacrimation
How to Increase Blood Pressure
- less stretching of the baroreceptors
- sympathetic stimulation
- peripheral vasoconstriction and increase vascular resistance
- increase blood pressure
How to Decrease Blood Pressure
- increased blood pressure
- increased stretching of the baroreceptors
- inhibition of sympathetic-mediated vasoconstriction
- decreases vascular resistance
- decreases blood pressure
How does the Sympathetic NS increase Heart Rate?
by increasing SA node discharges, conduction of impulses, and contraction of the ventricles and atria
What are the effects of an increase in BP and HR?
increased blood flow and oxygen supply to skeletal muscles
Where is the sinoatrial node?
right atrium
Where are the stretch receptors?
wall of the internal carotid artery and aorta
How does the Parasympathetic NS decrease heart rate?
by decreasing SA node discharges
What is pupillary constriction mediated by?
parasympathetic activation (pupillary light reflex pathway)
What is pupillary dilation mediated by?
sympathetic activation (Horner’s Pathway)
Pupil Constriction
- light into eyes
- goes through optic nerve to optic chiasm.
- crossover to pretectal nucleus
- to CN III
- Leaves prasympathetic nucleus to oculomotor nerve to constrict eyes
Pupil Dilation
- Comes from hypothalamus
- follows tectotegmental spinal pathway to preganglionic sympathetic neurons (T1-T3)
- Through cervical spinal cord
- sympathetic nerve goes to smooth muscles of periorbital area, eyelids
Micturition
ability to urinate
Sympathetic Bladder Innervation
Hypogastric nerve
Location of Hypogastric Nerve
L1-L4 in dog, L2-L5 in cat
Receptors of Hypogastric Nerve
- beta receptor- stimulation relaxes detrusor muscle to store urine
- alpha receptor-stimulation constricts internal urethral sphincter (smooth muscle)
- sensory branches to perceive pain
Parasympathetic Bladder Innervation
pelvic nerve
Location of Pelvic Nerve
S1-S3
Somatic Innervation of the Bladder
pudendal nerve
Location of Pudendal Nerve
S1-S3
Receptor to Pudendal Nerve
acetylcholine receptor. Simulation constricts external urethral sphincter. Sensory and motor to external urethral sphincter (skeletal muscle)
Brainstem control of micturition
Pontine Micturition Center
Where is the pontine micturition center?
reticular formation
What are the functions of the pontine micturition center?
- storage and evacuation
- receives information from spinal cord regarding bladder
- sends information to the bladder via spinal cord (reticulospinal tracts)
Conscious control of micturition
cerebrum
Inhibitory influence on micturition
cerebellum
Spinal cord control of micturition
reticulospinal tracts. Terminate in ventral horn gray matter. LMN to bladder
To store urine
- facilitation of pudendal nerve to contract the external sphincter muscle
- facilitation of hypogastric nerve to alpha receptors to contract internal sphincter muscle and beta receptors to relax detrusor muscle further
- Inhibition of pelvic nerve to detrusor muscle to allow relaxation
Process of Micturition
- inhibition of hypogastric nerve (beta receptors on detrusor, alpha receptors on internal sphincter m.)
- inhibition of pudendal nerve to relax external sphincter
- facilitation of pelvic nerve to contract detrusor
Sympathetic Innervation of Defecation
input from hypogastric nerve and L1-L4/L5 spinal cord segments. Innervated descending colon, rectum, and internal anal sphincter- excitatory to internal anal sphincter but inhibitory to descending colon and rectum
Parasympathetic Innervation of Defecation
input from pelvic nerve, S1-S3 spinal cord segments. Innervates descending colon and rectum
Somatic Innervation of Defecation
Input from pudendal nerve and S1-S3 spinal cord segments. Innervates striated muscle of the external anal spincter
Fecal Continence
- As colon fills, pressure stimulates sensory branch of pelvic nerve and that sensory information is sent to spinal cord, and subsequently to the brainstem (pontomedullary centers) and cerebral cortex
- Facilitation of the pudendal nerve causing contraction of the external anal sphincter
- Facilitation of the hypogastric nerve causing contraction of the internal anal sphincter
- inhibition of the pelvic nerve, causing relaxation of the colon and rectum
Defecation Process
- Full colon results in stretch of colon and rectum, which causes ascending sensory information to travel via pelvic nerve to spinal cord, brainstem, and cerebrum
- signal to activate defecation is sent to brainstem, descends spinal cord via reticulospinal tracts
- inhibition of the hypogastric nerve causing relaxation of colon and internal anal sphincter
- inhibition of pudendal nerve causing relaxation o the external anal sphincter
- facilitation of pelvic nerve, causing contraction of the colon and rectum
Loss of sympathetic supply to the eye
Horner’s Syndrome
Classical Signs of Horner’s Syndrome
- miosis
- ptosis
- enophthalmos
- 3rd eyelid protrusion/rpolapse
- +/- associated with loss of vascular tone on affected side vasodilation (warm skin, sweating)
Causes of Horner’s Syndrom
any lesion along the path of the sympathetic innervation to the eye; can also be idiopathic
causes irreversible inhibition of acetylcholinesterase
organophosphate toxicity
causes reversible inhibition of acetylcholinesterase
carbamate toxicity
Clinical signs of carbamate and organophosphate toxicity
- excessive parasympathetic stimulation (muscarinic crisis)
- bradycardia
- salivation
- lacrimation, miosis
- increase bronchial secretion
- urine dribbling
small pupil
miosis
Drooping of eyelid
ptosis
Sunken eye
enopthalmos
muscle twitching, tremors
nicotinic crisis
anxiety, restlessness, seizures
central stimulation
Function of the Cerebellum
- Does not initiate movement
- Coordinates movement, especially in relation to distance
- important in vestibular function
Layers of the Cerebellum
molecular, purkinje, granular
Pathways of Input
- Mossy fibers to granular layer
2. climbing fibers to molecular layer
Pathways of Output
inhibitory, GABA
Regions of the cerebellum
- spinocerebellum in middle
- Cerebrocerebellum on outside
- Vestibulocerebellum underneath
proper execution of coordinated movement
Spinocerebellum
planning coordinated, properly timed movement sequences
cerebrocerebellum
Coordinated balance and eye movement
vestibulocerebellum
Cerebellar Dysfunction
- Generalized ataxia
- Dysmetria, especially hypermetria
- intention tremor
- Vestibular Dysfunction
abnormal movements related to distance
dysmetria
movements bigger than they have to be
hypermetria
tremor when they intend to carry out purposeful movement. Only seen with cerebellar lesion
intention tremor
rhythmic oscillation of body part caused by alternating contractions of antagonistic muscles
tremor
cerebellum doesn’t form normally in fetus. Born with cerebellum that is too small. Can be caused by panleukopenia in cats, parvo in dogs, viruses in cattle, or genetic disease in Arabian horses
Cerebellar hypoplasia
composed of epithelium and internal elastic lamina. Endothelium is simple squamous composed in contact with blood.
Tunica intima
mostly smooth muscle, thickness varies with type of vessel. May have elastic fibers, may have external elastic lamina.
tunica media
outer layer. Connective tissue (collagen) that is blue on trichrome stain. Blends with and anchors to surrounding tissue.
tunica adventitia
Components of the Tunica Adventitia
vasa vasorum, nervi vasorum, adipose tissue
small vessels that supply large vessels
vasa vasorum
nerve supply to large blood vessels.
nervi vasorum
high pressure vessels that take blood away from the heart
arteries
Types of Arteries
elastic arteries, muscular arteries, and arterioles
aorta and largest branches. Tunica media contains lots of elastic fibers that are squiggly bright pink fibers. Cells between elastic fibers are smooth muscle
elastic arteries
medium-sized arteries. Tunica media is muscular. Very common
muscular arteries
less than 3 layers of smooth muscle cells. Small diameter. Innervated by sympathetic nervous system. Regulate blood flow into capillaries via capillary sphincter
arterioles
consist of endothelium and basement membrane only. No muscle. almost every cell in the body has a capillary nearby. Erythrocytes are often single file
capillaries
What happens at capillaries?
oxygen, nutrients, and carbon dioxide diffuse.
What is the most numerous type of vessel?
capillary
Types of Capillary
continuous, fenestrated, and discontinuous.
How to identify type of capillary
by location
complete basement membrane. Complete endothelial cells joined by tight junctions. Allows gas transport.
Continuous capillary
Where are continuous capillaries found?
muscle, brain, lung
complete basement membrane. Holes in endothelial cells allow for substantial transport of fluid, ions, hormones, and nutrients.
Fenestrated capillary
Where are fenestrated capillaries found
instestine, glomeruli, endocrine glands
incomplete basement membrane and endothelial cells. Large molecules and cells can pass through gaps
Discontinuous capillary
Where are discontinuous capillaries found?
Liver (sinusoids), spleen (sinuses), lymph nodes (sinuses), bone marrow, placenta
low pressure vessels that take blood towards the heart
Veins
Types of Veins
venules, medium-sized veins, large veins
thin walled, lack a tunica media.
venules
How to differentiate a venule from a capillary
by diameter
thin muscular tunica media. Valves for one-way flow. More irregularly shaped than artery.
medium-sized veins
thin muscular tunica media. Valves to prevent blood from flowing back into capillaries.
large veins
What is the venous partner to the arteriole?
venule
What is the venous partner to the muscular artery?
medium-sized vein
small mineralizations of the intima of the submucosal intestinal vessels in horses. Significance is unknown
intimal bodies
What is the endocardium made of?
simple squamous epithelium
malignant tumor of endothelial cells that tends to occur in the right atrium of dogs
hemangiosarcoma
cardiac muscles- striated with central nuclei and branching myocytes. Purkinje fibers
myocardium
heart bone in cattle
os cordis
Has adipose tissue, coronary arteries, and is covered in mesothelium
epicardium
How are flat mesothelial cells distinguished from endothelial cells?
by location
thin collagen layer with mesothelium on both sides. may contain adipose tissue
pericardial sac
Layers of the pericadrium
parietal and visceral layers
contain lymph fluid and lymphocytes
lymphatic vessels
thin-walled and have valves. Look similar to veins
lymphatic vessels
Lymphatic Capillaries Direction of Flow
Fluid flows toward heart only
Components of Lymphatic Capillaries
discontinuous endothelial cells and basement membrane
Main function of lymphatic capillaries
constantly pick up fluid, protein, and cells from interstitium and return it to the circulatory system
What uses lymphatic vessels to metastasize?
carcinomas
Largest lymphatic vessel
thoracic duct (left lymphatic duct)
component of cartilage. Live in lacunae. Secrete matrix.
chondrocytes
Types of Cartilage Growth
- appositional
2. interstitial
expansion from periphery. Continues throughout life. From perichondrium. Source of stem cells
appositional growth
outer layer of cartilage responsible for appositional growth.
Perichondrium
Does articular cartilage have a perichondrium?
no, so it cannot continue growing
expansion from within. Matrix and cell numbers increase. result in isogenous group. Most important in young animals
Intersitial Growth
multiple cells in a cluster, characteristic of interstitial growth
Isogenous Group
Types of Cartilage
- Hyaline
- Elastic
- Fibrocartilage
glassy. Found in fetal skeleton and articular surfaces of bone
Hyaline cartilage
Locations of Hyaline Cartilage
respiratory tree- nose, larynx, trachea
has elastic fibers between chondrocytes.
elastic cartilage
How to visualize elastic fibers in elastic cartilage?
cannot see on routine stain, need elastin stain
Locations of Elastic cartilage
pinnae, external ear canal
cartilage mixed with dense collagen. Chondrocytes are in rows
Fibrocartilage
Locations of Fibrocartilage
menisci, intervertebral discs, tendon and ligament attachments to bone
Components of bone
cells and matrix
Types of bone cells
osteoblasts, osteocytes, and osteoclasts
produce bone. Polygonal cells in rows along bone surface. Secrete and mineralize osteoid
Osteoblasts
unmineralized bone
osteoid
remove bone. Multinucleated giant cells of bone marrow origin. Bone removal occurs along brush or ruffled border.
Osteoclasts
depression in bone formed by osteoclast
Howship’s Lacunae
Types of Matrix
mineral and collagen
the majority of the bone is mineral. Mineral gives bone its rigidity
mineral matrix
polarized light required to see collagen. Gives bone its tensile strength.
collagen matrix
Microscopic Organization of Bone Collagen
woven bone and lamellar bone
immature bone. Formed during growth and repair. haphazardly arranged collagen fibers
woven bone
mature bone. Parallel collagen fibers.
lamellar bone
cylinders of concentric lamellae. Haversian canals at center of osteon. Blood vessels and nerves within canal. Stronger than woven bone
osteon
Configuration of Bone
compact and cancellous
solid bone with minimal marrow. Can be woven or lamellar. Cortex of adult bone is compact lamellar
compact bone
Trabeculae arranged in a 3 dimensional lattice. More bone marrow spaces than compact bone. Can be woven or lamellar. Present inside bone medullary cavity
cancellous bone
end of bone, covered with articular cartilage
epiphysis
clear line. Growth plate made of cartilage only present in growing animals
physis
cone-shaped transition between diaphysis and epiphysis
metaphysis
cylindrical shaft of bone that contains nutrient foramen
diaphysis
opening for blood vessel to come in in bone
nutrient foramne
contains hematopoietic cells. Becomes increasingly fatty with age
marrow
fibrous outer bony envelope. contains osteoprogenitor cells. Involved in repair and remodeling
Periosteum
Where does osteosarcoma occur
in metaphysis
inner bony envelope
endosteum
Types of Ossification
- endochondral ossification
2. intramembranous ossification
replacement of hyaline cartilage template by bone. Bone formation within cartilage
Endochondral Ossification
Layers of Physis inEndochondral Ossification
- Resting chondrocytes
- Proliferating chondrocytes that look like stack of coins
- Hypertrophied chondrocytes. Cells are swollen. Weakest zone
mineralized to form woven bone which covers remaining cartilage cores
osteoid
Fractures in physis. Affect bone growth in young animals
Salter-Harris Fractures
replacement of mesenchymal template by bone. Bone forms from condensed mesenchymal cells. Cartilage is not involved
Intramembranous Ossification
What determines bone density?
weight bearing
Types of Joints
- fibrous
- cartilaginous
- synovial
bones connected by dense collagen
Fibrous joints
bones connected by fibrocartilage
Cartilaginous Joints
ends of bones covered by hyaline cartilage. Bones connected by ligaments (attached to bone by fibrocartilage) and fibrous joint capsule.
Synovial Joints
Lines the inside of joint and inside of tendon sheaths.
Synovial Membrane
produce synovial fluid
synoviocytes
lubricates joint
synovial fluid
Another name for muscle cells
muscle fibers
outer membrane of the muscle fiber. Equivalent to the plasma membrane of a regular cell
sarcolemma
contractile units that make up the myofibrils. Have discs at each end called Z disks
sarcomere
protein that binds tropomyosin and actin. Has an affinity for calcium ions
troponin
thin protein filaments that attach to the z discs and extend toward the center. Intertwines with tropomyosin. Troponin bound intermittently
actin
thick filaments suspended among the actin. Resembles a golf club with globular heads that can bind ATP and actin
myosin
surrounds the myofibrils in a reticulated network. Stores calcium during contraction
sarcoplasmic reticulum
invaginations of the sarcolemma that transverse the network of myofibrils similar to poking straws into a bowl of spaghetti noodles. Filled with extracellular fluid and aid with action potential depolarization
T Tubules
Sarcomere Organization
- Z-line
- I-band
- A-band
- H-zone
- M-line
forms periphery of sarcomere where thin actin filaments attach.
Z line
light area, only actin
I band
dark area with actin and myosin overlapping
A band
center light zone, only myosin
H zone
middle of myosin
M line
Action Potential
- acetylcholine is released at the NMJ
- activates nicotinic acetylcholine receptors on sarcolemma
- Voltage gated Na ion channels open
- action potential spreads
- calcium released from sarcoplasmic reticulum
- contraction initiated
Other name for milk fever
parturient paresis
state of semi-paralysis seen in dairy cows after calving. Fewer calcium ions are available at the NMJ and less acetylcholine is released from the axon end. Less acetylcholine means less depolarization of the sarcolemma
milk fever
Excitation-Contraction Coupling
- increased calcium in sarcoplasm
- additional calcium binds troponin
- tropomysin moves deeper in groove- exposes myosin binding site on actin
shortening of muscle fibers without an action potential. Actin and myosin remain contracted because there is not enough ATP to release the myosin head
rigor mortis
hypocalcemia following whelping. Dogs differ from cows at the NMJ in that calcium deficiency causes voltage-gated Ca and Na to become more permeable to sodium. The influx of sodium make the membrane less polarized (less negative) and this means less stimulus is needed for depolarization. The nerve fibers become more excitable and discharge repetitively. This results in tetanic muscle contractions.
Puerperal tetany
Skeletal Muscle Fiber Types
- Type I slow twitch
- Type II fast twitch
- intermediate fibers with characteristics of I and II
slow twitch. Darker color due to myoglobin. Rich blood supply. More mitochondria. More aerobic
Type I muscle fiber
Fast twitch. Larger fibers with expansive sarcoplasmic reticulum. Fewer mitochondria, less extensive blood supply, fatigue quickly.
Type II muscle fibers
intermediate between fast and slow twitch
Type IIA
traditional fast twitch fibers
Type IIB
one alpha motor neuron and all the striated muscle fibers it innervates. The muscle fibers are the same type and will contract at the same time.
motor unit
increase the number of motor units firing at the same time
spatial summation
increase the frequency of motor unit activation
temporal summation
striated involuntary muscle cells. Have a single nucleus per cell and are connected to each other by junctions called intercalated discs
myocardial cells
How many nuclei does a skeletal muscle cell have?
multiple
Where are the nuclei in a skeletal muscle cell
at periphery
How many nuclei are in a cardiac muscle cell?
1
Where are the nuclei in cardiac muscle cells?
central
no visible striations, no T tubules, less developed sarcoplasmic reticulum. Can receive input from more than one neuron, autonomic
smooth muscle cells
contract independently. Each fiber innervated separately. Allows for fine movement. Found in the iris
Multiunit Smooth Muscle Cell
communicate and contract in a coordinated manner. Important for intestinal, uterine, and urethral contractions
Single-Unit Smooth Muscle Cell
Smooth Muscle Stimuli
mechanical pressure, blood pH, oxygen status, and extracellular ion concentration
found along the nerve fiber of smooth muscle. Releases acetylcholine (parasympathetic) or norepinephrine (sympathetic) diffusely along a muscle fiber sheet
variscocities
Smooth Muscle Contraction
- Intracellular concentrations of calcium increase when calcium enters the cell and is released from the sarcoplasmic reticulum
- Calcium binds to calmodulin
- Activates myosin light chain kinase
- MLCK phosphorylates light chains in myosin heads and increases myosin ATPase activity
What shape are smooth muscle cells
spindle-shaped with single nuclei packed closely
Which muscles have striations?
skeletal and cardiac
Contraction Mechanism of Skeletal Muscle
Ca binding to troponin C exposes myosin binding site on actin
Contraction Mechanism of Cardiac Muscle
similar to skeletal muscle
Contraction Mechanism of Smooth Muscle
Ca binds calmodulin, triggers MLCK mediated phosphorylation of myosin and actin binding
measure the strength of muscle contraction. Used to determine if paresis or paralysis is from issues with the CNS, NMJ, motor neuron, or skeletal muscle
electryomyogram
when myosin is bound to actin
cross-bridging
