quiz 2 A&P- Bones (intramembranous, Wolff's law, bone strength, Bonne health), joints Flashcards
know the vocab:
articulation
arth-
articulation- A joint, also known as an articulation, is a location where two or more bones meet. Most joints contain a single articulation. Each articulation contains the names of two bones (or sockets)
arth- The prefix (arthr- or arthro-) means a joint or any junction between two different parts
axial vs appendicular skeleton
axial bones: skull, neck, vertebrae, ribs, sacrum
appendicular bones: shoulders, arms, legs, feet, hands, and pelvis not including the sacrum
can you identify all the parts of the skeleton (axial & appendicular) yet?
yes!
if not, go and do that and come back
hyoid
the only bone in the body that does not articulate with another bone
ways to classify joints
what they are made of (the type of tissues) and how they move
what kind of tissue(s) are found at the joint?
fibrous joints
cartilaginous joints
synovial joints
fibrous joints
generally synarthrotic
synovial joints
generally diarthrotic
what types of movement are allowed in joints
synarthroses
amphiarthroses
diarthroses
synarthroses
no movement, tight together so no movement
amphiarthroses
partially moveable
diarthroses
fully moveable
finger and hip joints
details on fibrous joints
-fibrous joints join bones
- generally synarthroses(so these joints do not move)
- 3 subtypes: sutures, syndesmoses, gomphoses
sutures
-lines that connect the parts of the skull
-this joint is held together with very short, interconnecting fibers and bone edges interlock
- synostosis- closed suture, from fibrous tissue ossification,
-synarthroses joints
-there are also facial sutures not just cranial
-dense regular connective tissue fibers are continuous with the periosteum (which itself has dense irregular connective tissue)
-craniosynostosis- a birth defect in which the bones in a baby’s skull join together too early
what are syndesmoses (syndesmosis)
-amphiarthrotic joints
-a joint held together by a ligament
-fibrous tissue can vary in length but is longer than in sutures
-a fibrous joint in which two adjacent bones are linked by a strong membrane or ligaments.
-ball and socket joint.
-made of dense regular collagenous tissue
-For ex: between the radius and ulna, there is a syndesmosis that is made of dense regular collagenous tissue
what are gomphoses (a gomphosis)
- found only in teeth
-a fibrous mobile peg-and-socket joint. The roots of the teeth (the pegs) fit into their sockets in the mandible and maxilla and are the only examples of this type of joint.
-they are synarthrotic joints- so they do not move!
-the peg fits into the osseous pocket, and into the socket of the alveolar process
-the teeth are connected by the periodontal ligament
cartilaginous joints
-the bones are joined together by the cartilage tissue
-there are 2 types: synchondroses and symphyses
synchondroses
-one of the two types of cartilaginous joints (can you name the other one?)
-these are synarthrotic, so they do not move
-the name translates to together cartilage
-syn: together
-an example is hyaline cartilage which is articular cartilage that is found on both epiphyses of the long bone- so it is a cartilaginous joint and specifically a synchondroses because it will connect the long bone to other bones using the synchondroses joint
-hyaline cartilage is found in synchondroses
-singular: synchondrosis
-examples of synchondroses: epiphyseal plates of the long bone
-the mobility of these joints is synarthrotic
-another example of synchondroses joints: costochondral joints (between the ribs and rib cage) and first sternocostal joints (between the first rib and sternum)
what is found in symphyses cartilaginous joints?
-fibrocartilage which have collagen fibers and chondrocytes in the lacunae
symphyses
-singular: symphysis
-bones are united by fibrocartilage
-in the public symphysis- the two ox coxae (or hip bones) are joined together with fibrocartilage
-in pregnancy, a hormone releases for the symphysis to move so hips can widen
-another example of symphyses joint (fibrocartilage)- the intervertebral joint which contains a fibrocartilaginous intervertebral disc (sandwiched between hyaline cartilage)
-note: there is still hyaline cartilage at bone surfaces, fibrocartilage is in between
intervertebral disc
-contains two parts: annulus fibrous and nucleus pulposus
-annulus fibrous are a ring of fibers on the outer part of the intervertebral disc (ring)
-nucleus pulposus are gelatinous inner part of intervertebral disc (center)
herniated disc (AKA slipped di, prolapsed disc)
what happens:
annulus ruptures
nucleus protrudes through (pokes through)
parts of the spinal cord at their curvature names
cervical curvature (concave)- the neck, C1 to C7 bones- secondary curvature!
thoracic curvature (convex)- the rib cage, T1 to T12 bones- primary curvature
lumbar curvature (concave)- the mid-back- L1 to L5 bones, secondary curvature
sacral curvature (convex)- lower back, sacrum, and coccyx, primary curvature
the vertebrae column has many curvatures
remember the names of C1 and C2. vertebrae? These form a diarthrotic synovial joint. What does that tell you about their mobility?
C1- Atlas
C2- Axis
diarthrotic synovial joint- full moveable joints
meaning of primary and secondary curvatures
primary curvatures- are present at birth (the thoracic and sacral curvatures)
secondary curvatures- are not present at birth (the cervical and lumbar curvatures)
cervical curvatures develop after birth when the infant starts to hold up their head
lumbar curvatures develop when the baby is standing and walking
newborns only have the primary curvatures
scoliosis, lordosis, kyphosis
scoliosis- a sideways curvature of the spine that most often is diagnosed in adolescents.
lordosis- excessive inward lumbar curvature of the spine usually caused by and common in pregnancy.
kyphosis- an exaggerated, forward rounding of the thoracic curvature, usually caused by osteoporosis
synovial joints
-freely moveable aka, diarthrotic
-different structure than fibrous and cartilaginous joints, although they may have similar components
-fluid-filled to make a friction-free surface
what types of movements are allowed at synovial joints?
Gliding
Flexion, Extension
Hyperextension
Abduction, Adduction
Circumduction
Rotation
Pronation , Supination
Inversion, Eversion
Opposition
Protraction, Retraction
what are the components of the synovial joints
articular cartilage
fibula
tibia
articular capsule:
(joint space containing synovial fluid
synovial membrane-where synoviocytes are made (inner layer)
fibrous outer layer)
femur
periosteum
what else is present in the synovial joint structure
Reinforcing ligaments
capsular ligaments
continuous with fibrous layer of articular capsule
extra- or intracapsular ligaments
one type is deep to the capusle, one is outside. Which is which?- extra: out, intra: deep
ligament
articular capsule
periosteum
Rheumatoid Arthritis
0.5% - 1% of people in developed world
Cause? Probably multifactorial (like most things…)
some genetic risk factors
environmental risk factors may include infection and smoking
-Autoimmune disease- immune system attacks own self, treats what is in the joints are foreign and attacks itself
Articular, extra-articular and systemic effects
Brief info about adaptive immunity (B and T cells)
-B cells
If a B cell encounters an antigen, it will proliferate and start making lots of antibodies against that antigen
-make antibodies-tag + bind to foreign things
Antibodies “tag” foreign cells or particles, marking them to be destroyed/engulfed.
-T cells
Activated T cells respond to foreign antigens that are presented to them by an antigen presenting cell.
Remember from our skin health discussion?- yes macrophages and dendritic cells do this
T cells can secrete cytokines and affect activity of other immune cells.
cytokines are proteins that act as messengers between immune system components
in RA
Synovitis = inflammation of synovial membrane. Caused by infiltration of immune cells and angiogenesis
Synovial membrane becomes hyperplastic, expands
Osteoclast rich region of the synovial membrane destroys bone.
3a) Enzymes destroy cartilage.
Potential results of RA
At Joints
Scar tissue formation
Scar tissue ossification
Loss of joint mobility (ankylosis)
Systemic effects possible
Anemia
Cardiovascular disease
Osteoporosis
Fatigue
Depression
Other types of arthritis?
Osteoarthritis
“wear and tear”
Age-related
Articular cartilage breakdown
Gouty arthritis (Gout)
Uric acid (normal waste product) rises in blood
Crystals form in soft tissues of joints
Elements of signaling
Signal (from outside the cell)
Proteins, steroids, other molecules; could be hormonal (long distance) or paracrine (short distance)
Receptor (cell)
Membrane proteins or intracellular proteins
Signal transduction (inside the cell)
Note that Gap junctions may transmit second messengers and intracellular signaling molecules from cell to cell.
Response
Examples: altered metabolism, proliferation or even perhaps apoptosis
Bone as a reservoir for blood Ca2+
involves bone remodeling
Calcium information:
Human body has how many grams of Ca2+
What is Ca2+ necessary for in the body?
-Human body has 1200-1400 g of Ca2+
-What is Ca2+ necessary for in the body?- Muscle contraction, neuronal functions, signaling
-Just because you eat a lot of calcium does not mean that they are absorbed and entering into your blood stream to eventually get to your bones
-so you eat, then your food goes to your digestive system and there are blood vessels adjacent to your digestive system so the calcium from the food can be absorbed into the blood
Calcium information:
Human body has how many grams of Ca2+
What is Ca2+ necessary for in the body?
-Human body has 1200-1400 g of Ca2+
-What is Ca2+ necessary for in the body?- Muscle contraction, neuronal functions, signaling
-Just because you eat a lot pff calcium does not mean that they are absorbed and entering into your blood stream to eventually get to your bones
-so you eat, then your food goes to your digestive system then it goes out, but there are blood vessels adjacent to your digestive system so the calcium from the food can be absorbed into the blood
-taking vitamin D increases the absorption of the Ca2+ into the blood from the intestine
Where is Ca2+ found?
-99% in bones
-9-11 mg/dl of blood
(9-11 mg/100 ml blood)
We get Ca2+ from our diet but what helps the Ca2+ get into the blood to get into the bones?
Vitamin D is necessary for absorption across intestine to blood stream.
Remember Vitamin D production and activation?
Which tissues and organs are involved?
1- UV + Cholesterol make the Vitamin D precursor
2- The precursor (made by skin cells) goes to the liver to be modified, then goes to the kidney
3- full activation in the kidney
6.15 Maintaining homeostasis: response to low blood calcium ion level by a negative feedback loop.
1- stimulus- the blood Ca2+ decrease below normal range
2- receptor- parathyroid gland (in the thyroid) cells detect a low blood Ca2+ level
3- control center- parathyroid gland cells release PTH (parathyroid hormone) into the blood; PTH is released when the blood Ca2+ is too low
4- effector/response- Osteoclasts resorb bone; they dissolve the bone matrix (osteoid) to release Ca2+ to the blood, kidneys retain Ca2+ (so it is not lost from blood via the urine), intestines absorb Ca2+ to go into the blood
An added wrinkle to PTH
PTH recruits and activates osteoclasts to promote matrix break-down.
But it also can promote bone formation (osteoblasts).
Signaling systems are complex!
what happens in Bone marrow:
hematopoiesis (blood cell formation) & fat storage
hem-
heme-
hemat-
refers to blood
-poiesis: to make
Red marrow is found
in spongy bone and medullary cavities in children; everywhere.
In adults, red marrow is more restricted to the epiphyses
This is a reminder that children are not just mini versions of adults! Their anatomy and physiology is unique!
endochondral ossification
1- chondroblasts become mitotic
2- chondroblasts become amitotic
3- chondroblasts expand by hyperplasia and mature
4- chondroblasts die then their matrix is calcified and the dead and expanded condroblasts are now replaced by Bone
osteoblasts
synthesize bone matrix by secreting it; bone builders
osteoclasts
cells that degrade bone to initiate normal bone remodeling; bone breakers
osteocytes
the cells residing within the bone matrix and comprising 90% to 95% of the all bone cells; mature bone cells; maintain bone
signals for bone growth
and
why do we need to exercise
growth hormone and sex hormones
why must exercise because exercise puts stress on our bones and this stress helps our bones become stronger
Factors that influence bone remodeling.
increased osteoblasts activity:
-compression load or exercise
-tension placed on bone
-adequate dietary intake of calcium and vitamins C, D and K
Increase osteoclast activity:
-continuous press placed on bone
-parathyroid hormone
-decrease in blood calcium ion concentration
decreased osteoblasts activity:
-inadequate exercise
-inadequate dietary intake of calcium or vitamins C, D and K
decrease osteoclast activity:
-estrogen
-calcitonin
-increase in blood calcium ion concentration
Bone repair
-What cells are involved?
-How is this similar to or different from growth and development of bones?
-What is osteogenesis coupled with?
What cells are involved?- osteoblasts and osteoclasts
How is this similar to or different from growth and development of bones?- similar in that both involve blasts and clasts; bone growth is the increase in the diameter of bones by the addition of bone tissue at the surface of bones. Bone remodeling involves the processes of bone deposition by osteoblasts and bone resorption by osteoclasts. Bone repair occurs in four stages and can take several months.
What is osteogenesis coupled with?- angiogenesis
Fractures result from…
result from trauma, or may be a result of weakening/thinning bones (why is it important to keep physically active in old age? What does this mean for bone health?– stress on bones makes for stronger and healthier bones)
Fractures can be classified in many ways:
displaced vs. nondisplaced (refers to bone end position)
complete vs. incomplete (does the break in the bone go through the middle?)
open (compound) or closed (refers to skin penetration)- does the bone go through skin?
What is Vitamin D is important for?
Ca2+ absorption in gut (from diet)
Regulating calcium and phosphate use
Poor mineralization of bones:
osteomalacia
rickets
osteomalacia
Soft, weak bones; Pain upon bearing weight
Rickets
(osteomalacia of children)
Bowed legs and other bone deformities
Bone ends enlarged and abnormally long
Cause of poor mineralization of bones:
malnutrition of Ca2+ and vitamin D
for Poor mineralization of bones what is more active /inactive
-osteoblast activity decrease
-osteoclast activity increase
Osteoporosis (Group of Diseases)
Bone resorption outpaces deposit
Spongy bone of spine and neck of femur most susceptible
Vertebral and hip fractures common
Risk Factors for Osteoporosis
Most often aged, postmenopausal women
30% of women 60 – 70 years of age; 70% by age 80
Occurs less often in men
Sex hormones maintain normal bone health and density
As secretion wanes with age osteoporosis can develop
Some Risk Factors for Osteoporosis
Diet poor in calcium and protein
Insufficient exercise to stress bones
Immobility
Also:
Smoking
Hormone-related conditions
Thyroid problems
Diabetes mellitus
Men taking androgen-suppressing drugs
Arthritis
This is joint disease
arth- refers to joints (think arthropods and their jointed appendages)
-itis means inflammation
what makes up the central nervous system (CNS) and peripheral nervous system (PNS)
CNS- brain and spinal cord
PNS is everything else
ANATOMICAL TERMS TO KNOW FOR CNS
Gyrus (raises of the brain)
cortex (below the gyrus– gray matter)
sulcus (indents of the brain)
fissure (deeper indents of the brain; deep sulcus)
white matter–deep to the white mater
left & right cerebral hemispheres
transverse cerebellum fissure (fissure that separates the cerebellum from the cerebrum)
cerebellum (little brain; controls voluntary motion)
parietal-occipital sulcus (one medial surface of hemisphere)
lateral sulcus
occipital lobe
temporal lobe
central sulcus
frontal lobe
pons
medulla oblongata
some more vocab of the brain
frontal, parietal, occipital, temporal lobes
lateral fissure (deep fissure in each hemisphere that separates the frontal and parietal lobes from the temporal lobe)
central sulcus
pre-central gyrus
postcentral gyrus
anterior (where the frontal lobe is)
posterior (where the occipital lobe is)
few more vocab of the brain
parieto-occipital sulcus
lateral sulcus
transverse cerebral fissure
cerebellum
pons
medulla oblongata
spinal cord
The nervous system: different terminology for the CNS & PNS
CNS
Tracts = bundles of neuron processes
Nuclei = clusters of cell bodies
PNS
Nerves = bundles of neuron processes
Ganglia = clusters of cell bodies
White & gray matter in the CNS
White matter = myelinated fiber tracts
Gray matter = cell bodies, dendrites, glia, non-myelinated fibers
-cerebral gray matter- looks gray
-cerebral white matter- looks white
Cerebral cortex
-outermost part of the cerebrum , gray matter (all neurons of the cortex are interneurons)
-There is also deep gray matter in the brain: basal nuclei
structure of cerebrum
-cerebral cortex
-basal nuclei
-limbic system
cerebral cortex
substructures:
-primary motor
-primary somatosensory cortices
-multimodal association areas
basal nuclei
caudate nuclei
putamen
globus pallidus
limbic system
-hippocampus
-amygdala
primary motor cortex function
-plans and executes the movement
-Conscious control of precise voluntary muscle movements
-Axons from here project to the spinal cord
-Somatotropy – the body is spatially represented in the primary motor cortex
primary somatosensory function
-receive and process different types of sensory input
-Concerned with conscious awareness of sensation
-Receives info from sensory receptors in the skin and inside the skeletomuscular system
We’ve talked about skin receptors!
-Neurons can identify the part of the body stimulated.
multimodal association areas function
-integrate sensory and motor information from a variety of different primary cortices
caudate nuclei
putamen
globus pallidus
function
regulate movement
hippocampus function
plays a role in memory and learning
amygdala
plays a role in behavioral expression and emotion
cerebellum function
coordinates voluntary function
motor and sensory areas
primary motor cortex
primary somatosensory cortex
primary motor cortex
-Conscious control of precise voluntary muscle movements
-Axons from here project to spinal cord
-Somatotropy – body is spatially represented in primary motor cortex
1° somatosensory cortex
-Concerned with conscious awareness of sensation
-Receives info from sensory receptors in skin and inside the skeletomuscular system
-We’ve talked about skin receptors!
-Neurons can identify part of body stimulated.
contralateral side of the body
Each cerebral hemisphere controls the contralateral (opposite) side of the body, as far as sensory and motor functions go.
brain cortex
the outermost layer of the brain that is associated with our highest mental capabilities.
homunculus
a representation of a small human being, that shows that the brain is not equal in representing the parts of the Body
what does the limbic system do
-memory
-learning
-emotion
coverings of the brain: meninges (singular: meninx)
-dural (durable/tough)
-arachnoid mater
-pia mater
dura mater has 2 sheets/parts
-periosteal dura
-meningeal dura
what does the brain have
-skull-outermost
-falx cerebri-indented tube
-dural sinus-hole at the end of the falx cerebri
-dura mater
-arachnoid mater
-pia mater
-dural sinus
-dural sinus (superior sagitall sinus)
spinal meninges and spinal cord components
-pia mater
-subarachnoid space (real space, CSF flows through)
-arachnoid mater
-subdural space (potential space)
-dura mater
difference of dura mater of the brain vs spinal cord
brain has periosteal dura and meningeal dura
but the spinal cord has just meningeal dura not periosteal dura
spinal meninges and spinal cord more components! (ex: what is upon the dura)
-epidural space: upon the dura, contains adipose tissue + veins
-dura mater
-pia mater
-subarachnoid space (real space, CSF flows through)
-arachnoid mater
-subdural space (potential space)
-denticulate ligament: pia mater used to secure spinal cord
Brain Functional Areas
There are discrete cortical functional areas = domains
Some functions (e.g. memory, language) are spread out over large areas of cortex
diencephalon
relays sensory information between brain regions and controls many autonomic functions of the peripheral nervous system.
parts of limbic lobe
-cingulate gyri
-parahippocampal gyrus
fornix
acts as the major output tract of the hippocampus, arcing around the thalamus and connecting the medial temporal lobes to the hypothalamus.
limbic system function
is the part of the brain involved in our behavioral and emotional responses, especially when it comes to behaviors we need for survival: feeding, reproduction, and caring for our young, and fight or flight responses.
-learning
-memory
-emotion
cerebellum main function
coordinates voluntary movement
cerebellar hypoplasia
is a neurological condition in which the cerebellum is smaller than usual or not completely developed. Cerebellar hypoplasia is a feature of a number of congenital (present at birth) malformation syndromes, such as Walker-Warburg syndrome (a form of muscular dystrophy.
sinus– cranial meninges
space or cavity or opening (mucus or air) in dura sinuses (there is one at the end of the falx cerebri and at the top of the falx cerebri below the dura mater, there is CSF
dural folds and dural sinuses
-dural sinuses contain CSF
-Superior sagittal sinus
-falx cerebri
-tentorium cerebellum
Structure of the cranial meninges and dural sinuses
-skull
-periosteal dura
-superior sagittal sinus
-arachnoid granulation- pokes through meningeal dura to the sinus for CSF to flow
-meningeal dura
-subdural space
-arachnoid mater
-subarachnoid space
-pia mater
-blood vessels- between the arachnoid trabeculae of the arachnoid mater
-cerebral cortex
-falx cerebri- meningeal dura that extends very deep
-dural sinus- at the end of the dural sinus
ventricles
spaces in brain that hold CSF
the ventricles + other structures
-lateral ventricles
-interventricular foramen
-posterior horns of lateral ventricles
-third ventricles
-cerebral aqueduct
-fourth ventricle
-inferior horns of lateral ventricles
-brainstem (midsagittal section)
how much CSF is there in the body and how is drained
-there is 150mL and 50mL is made every day
-it is drained thru arachnoid granulation to the dural sinus
where CSF is made and how flows
-CSF is made in the choroid plexus of each ventricle
1- fluid and electrolytes leak out of the capillaries of the choroid plexuses; the choroid plexus of each ventricle makes CSF
2- ependymal cells secrete CSF into the ventricles
3- CSF circulates through and around the brain and spinal cord in the subarachnoid space; CSF flows through the subarachnoid space
4- some of the CSF is reabsorbed into the blood in the dural sinuses via the arachnoid granulations; CSF is absorbed into the dural venous sinuses by the arachnoid granulation
what does the CNS consist of?
-brain and spinal cord
-brain and spinal cord integrate info.
peripheral nervous system (PNS)
what does the PNS consist of
cranial and spinal nerves link CNS and rest of body; perform motor and sensory functions; sensory (afferent) division and motor (efferent) division (info goes out of the CNS)
What comes to the sensory (afferent) division
info from the somatic sensory division (carries general sensory signals from muscles, bones, joints, and the skin, as well as special sensory signals) and information from the visceral division (carries signals from organs)
What comes to the motor (efferent) division
info from the somatic motor division (carries signals to skeletal muscles) and information from the autonomic nervous system (carries signals to smooth muscle, cardiac muscle and glands)
afferent
conducting or conducted inward or toward something (for nerves, the central nervous system; for blood vessels, the organ supplied).
What comes to the motor (efferent) division
info from the somatic motor division (carries signals to skeletal muscles) and information from the autonomic nervous system (carries signals to smooth muscle, cardiac muscle, and glands)
efferent
conducted or conducting outward or away from something (for nerves, the central nervous system; for blood vessels, the organ supplied).
“efferent neurons carry impulses outwards to the effector organs”
sensory
relating to sensation or the physical senses; transmitted or perceived by the senses.
integrative
serving or intending to unify separate things.
motor
giving, imparting, or producing motion or action.
visceral
Referring to the viscera, the internal organs of the body, specifically those within the chest (as the heart or lungs) or abdomen (as the liver, pancreas or intestines).
The dura mater covering is NOT anchored to vertebrae (there is an epidural space) how is this different from the brain?
missing periosteal
The spinal cord is thicker in some places than in others
where
cervical, lumbar enlargements-where the arms and legs are
The spinal cord ends around
L2 at the conus medullaris. Fibrous extensions of this anchor the cord into the tailbone.
The spinal cord ends around
L2 at the conus medullaris. Fibrous extensions of this anchor the cord into the tailbone.
L5 (only 5 bones)
how many pairs of spinal nerves (PNS) and what is the collection at the posterior end called
cauda equina, nerves that look like horse’s tail
review structure of spinal meninges
okay!
sampling CSF
The lumbar puncture needle enters through the subarachnoid space between the fifth lumbar and vertebrae (midsagittal-section)
epidural injections
go into the epidural space
general classes of cells in the nervous system
glia and neurons
glia cells
-small cells, supportive (don’t assume that that glia aren’t that important – they are critical to nervous system function!)
-4 types in CNS, 2 types in PNS
neurons
-Also called nerve cells
-Various structural and functional classifications
-Electrically active – can generate action potentials
Classification of neurons:
Functional
Structural
functional properties of neurons
-Sensory neurons
-Motor neurons
-Interneurons
cerebrospinal fluid (CSF)
what is it made of
what is it similar to
where does it circulate through
what is its function
what is it made of- blood plasma
what is it similar to- composition of blood plasma
where does it circulate through- ventricles, around the brain and in/around the spinal cord
what is its function- to provide cushion from concussion that comes from blows to the head
Structural properties of neurons
-Grouped according to number of processes extending from cell body
-General:
–Sensory neurons are pseudounipolar or bipolar neurons
–Motor neurons are multipolar neurons
why do neurons have extreme longevity (long long life)
Have to be long-lived because mostly they are amitotic
what does this mean?- that they do not multiply or go through mitosis
Is this always true?- no because in turtles, the eye neurons grow back but not in humans )
why do neurons have high metabolic rates?
Need lots of glucose
Need lots of oxygen
(glucose + oxygen will be used to make ATP)
Have wastes to get rid of
Need to have ATP supply- because they have to move a lot of things around
to run Na/K ATPase, molecular motors; produce lots of chemical communication signals (neurotransmitters)…
structural classes of neurons
multipolar-many sides
bipolar- two sides
pseudounipolar- one side
typical functions class of neurons
motor (afferent)neurons, interneurons
mostly neurons in the CNS, motor neurons in the PNS
general sensory neuron
they are sensory (afferent) neurons
general structure of neurons
receptive region
conducting region
secretory region
receptive region of neurons
dendrites and head
receiving info.
where cell receives neurotransmitters
conducting region of neurons
axon hillock and axon
where action potentials happens
secretory region
axon terminal
where signals are related to other cells
what could Target cells be
neurons
muscles
glands
Neuron structural components
dendrites- receive neurotransmitters
cell body (head)- los received neurotransmitters
axon hillock- connection of cell Boyd to axon
axon
myelin sheath
axon terminal- secretory region where neurotransmitters are secreted
CNS glial cells
Astrocytes
There are lots of different types of astrocytes.
Generalization of their role: They control the environment of the CNS (extracellular environment, physical and chemical environment of the neurons)
what are the 4 glial cells
astrocytes
microglia
oligodendrocytes
ependymal cells
oligodendrocytes
myelin sheath producers
myelin sheath
-covering of axon
-function: electrical insulation
-helps action potentials move faster down axon
-made in CNS by oligodendrocytes
microglia
-clean up crew
-also control the environment by picking up particles (garbage truck)
-doing phagocytosis
ependymal cells
what doe sit makes
where is it found
makes cerebrospinal fluid
found in choroid plexus
what makes myelin sheath in CNS
Oligodendrocytes
what makes myelin sheath in CNS
Schwann cells
Glial cells of the PNS
Schwann cells and satellite cells
satellite cells
Sort of analogous to the astrocytes of the CNS, control the environment around neurons
does the white or gray matter have
the white has myelin
the gray has myelin
What does the Schwann cell do around the cell
wraps around the cell many times to make the myelin sheath
neurolema
plasma membrane of neuron
axons are enclosed by
Schwann cells but Schwann cells don’t repeatedly wrap around them
what is multiple sclerosis?
loss of myelin so the action potential does not move as fast
so they do not move as fast
it is an autoimmune disease
membrane potential
distribution of charges across a membrane
movement of Na+ and K+ ions and their driving forces
Understanding membrane potential
Takes into account all charged particles, their distribution inside and outside of the cell
this in turn depends on driving forces and membrane permeability
Every cell has a membrane potential
resting membrane potential
the membrane potential of neurons and skeletal, and cardiac muscle when an action potential is not happening.
in general what are cells most permeable to
K+ because of the K+ leak channels that are always open and allow K+ to move out
there are few Na+ leak channels
so at rest mem. potential approx. equals Ek+
Measuring the resting membrane potential: general
put the microelectrode in the neurons and put the other side into a reference electrode
the microelectrode is connected to a voltage recorder
more on the permeability of the membrane
The membrane is most permeable to K (lots of K “leak channels” that are always open), so the resting membrane potential is quite close to the equilibrium potential for potassium. If it was only permeable to potassium, the resting membrane potential would equal the equilibrium potential for K. The membrane is slightly permeable to Na (some Na “leak channels that are always open). The movement of Na into the cell keeps the resting membrane potential slightly more positive than the K equilibrium potential.
Generation of the resting membrane potential:
major player is K+ leak channel
Movement through ion channels is passive or active?
passive- no ATP or other assistance needed
Ions move through channels when the channels are ___. The direction of net movement is determined by __________
Ions move through channels when the channels are open. The direction of net movement is determined by electrical and chemical driving forces.
Ion channels are generally selective for a particular ion
Na+ moves through Na+ channels, K+ through K+ channels, etc.
Ion channels can be closed or opened.
They do not all exist in a perpetually open state. (example of an exception: K leak channel)
gated ion channels can be opened in different ways– what they respond to to open?
what are the 3 ways
voltage-gated (opens in response to membrane potential)
ligand-gated (extracell. ligand) (open due to ligand)
ligand-gated (intracell. ligand) (open due to ligand)
mechanically gated (pulled open)
A few types of gated channels that are important in neurons:
chemically-gated (opens in response to binding of the appropriate neurotransmitter) and voltage-gated (opens in response to changes in membrane potential)
States of voltage-gated channels for K+ channels
there are 2 states:
1- activation gate closed- K+ can not move through
2- activation gate open- K+ can move through
States of voltage-gated channels for Na+ channels
there are three states:
1- activation gate is closed, inactivation gate open
2-activation gate is open, inactivation gate closed
3-activation gate is open, inactivation gate open- Na+ can go through
chemical synapses,
where neurons communicate
Communication between two neurons happens at the
synapse.
presynaptic cell, postsynaptic cell, synaptic cleft
presynaptic cell-cell before the synapse, usually secreting the neurotransmitter, postsynaptic cell-cell after the synapse usually receiving the neurotransmitters synaptic cleft- space of the synapse where the neurotransmitter travels
Neurons communicate chemically via _______ (signals released from the pre-synaptic neuron and that diffuse to the post-synaptic neuron).
neurotransmitters
These chemicals will determine if/when a post-synaptic neuron fires an action potential
Chemical synapses transmit signals from one neuron to another using
neurotransmitters
Neurotransmitter diffuses
across the synaptic cleft and
binds to specific receptors on
the postsynaptic membrane
they are exocytosed from vesicles once the Ca2+ channels are opened and they are opened by an AP that happens are the axon terminal that was propagated along the axon
What do neurotransmitters do in an active chemical synapse?
Bind to receptors on target cells
Open (or close) ion channels
The examples at right are ligand-gated channels
Change membrane potential
but in a resting chemical synapse the neurotrans. stay in the vesicles
depolarization
when the membrane potential becomes more positive and less negative because Na+ channels open as they can come into the cell
hyperpolarization
membrane potential becomes more negative
K+ flows out after the Na+ channels stay closed (they cannot reopen immediately so the action potential will only go forward)
What are the potential effects of neuro-transmitters on the postsynaptic cell?
post synaptic potentials
Excitatory post synaptic potentials (EPSPs)
Inhibitory post synaptic potentials (IPSPs)
Excitatory post synaptic potentials (EPSPs)
Depolarization of post-synaptic membrane
Inhibitory post synaptic potentials (IPSPs)
Hyperpolarization of the post-synaptic membrane
EPSPs and IPSPs at (receptive) areas of the membrane are summed across space and time.
What matters is what happens to the membrane at where?
What matters is what happens to the membrane at the axon hillock.
No summation:
2 stimuli separated in time
cause EPSPs that do not
add together.
Temporal summation:
2 excitatory stimuli close
in time cause EPSPs
that add together.
Spatial summation:
2 simultaneous stimuli at
different locations cause
EPSPs that add together.
Spatial summation of
EPSPs and IPSPs:
Changes in membrane potential
can cancel each other out.
Something to understand:
do neurotrans. cause EPSP or IPSP?
It is not the neurotransmitter itself that determines whether it is excitatory or inhibitory. It is the receptor at the post-synaptic membrane
A neurotransmitter that may be excitatory in one situation (if it binds to a receptor that will lead to postsynaptic membrane depolarization)
The same neurotransmitter could be inhibitory in another (if it binds to a receptor that will lead to postsynaptic membrane hyperpolarization)
The big picture of the action potential
1- resting state- -70mV
2-Depolarization (getting positive in the cell)- the threshold is reached and Na+ channels are opened
3-repolarization (getting negative in the cell)- Na+ channels close while K+ channels open
4- hyperpolarization (an excess of open potassium channels)
The major players for the generation of an action potential:
Voltage-gated Na+ channels
-opens for a little bit, then closes
Voltage-gated K+ channels
-opens later
A pre-synaptic neuron releases _____ onto a _____. If the ____ are excitatory, the _______ depolarizes at that area.
A pre-synaptic neuron releases neurotransmitters onto a post-synaptic cell. If the neurotransmitters are excitatory, the post-synaptic neuron depolarizes at that area.
There must be a stimulus that causes the membrane to depolarize to a certain THRESHOLD LEVEL
to get voltage-gated Na+ channels to open and an action potential to start.
Events of an action potential - summary from Amerman’s book.
1- local potential depolarizes the axolemma of the trigger zone
2- voltage-gated Na+ channels activate, Na+ enter, and the axon section depolarizes
3- Na+ channels inactivate and voltage-gated K+ channels activate so Na stop entering and K+ exit the axon–repolarization
4- Na+ channels return to the resting state and repolarization continues
5- the axolemma may hyperpolarize before K+ channels return to the resting state; after this, the axolemma returns to the resting membrane potential
speed of action potential propagation moving down the axon depends on:
1- diameter of the axon (larger mean faster)
2-myelin vs no myelin (if there is myelin then it will move faster)
AP happens at the gaps between the myelin
In bare plasma membranes, voltage decays.
Without voltage-gated channels, as on a dendrite,
voltage decays because current leaks across the
membrane.
In nonmyelinated axons, conduction is slow
(continuous conduction).
Voltage-gated Na+ and K+
channels regenerate the action potential at each point
along the axon, so voltage does not decay. Conduction
is slow because it takes time for ions and for gates of
channel proteins to move, and this must occur before
voltage can be regenerated.
In myelinated axons, conduction is fast (saltatory
conduction).
Myelin keeps current in axons
(voltage doesn’t decay much). APs are generated only
in the myelin sheath gaps and appear to jump rapidly
from gap to gap.
What happens when the AP arrives at the axon terminal?
1- Action potential
arrives at axon
terminal.
2- Voltage-gated Ca2+
channels open and Ca2+
enters the axon terminal
3- Ca2+ entry
causes synaptic
vesicles to release
neurotransmitter
by exocytosis
4- Neurotransmitter diffuses
across the synaptic cleft and
binds to specific receptors on
the postsynaptic membrane
5- The binding of neurotransmitters opens
ion channels, resulting in graded
potentials.
6- Neurotransmitter effects are
terminated by reuptake through
transport proteins, enzymatic
degradation, or diffusion away
from the synapse (next slide).
termination of synaptic transmission
diffusion and absorption- neurotrans. diffuse away from the synaptic cleft and are returned to the pre-synaptic neuron
degradation- neurotrans. are degraded by enzymatic rxns in the synaptic cleft
reuptake- neurotrans. are taken back into the presynaptic neuron
boundaries between these compartments
-blood (in vessels)
-CSF (in ventricles, subarachnoid
-ISF (interstitial fluid, the extracellular fluid, surroundings of all CNS cells)- extracellular to cells
movement of this material is controlled
-water
-ions
-large molecules and proteins
-immune cells
why is to important to tightly regulate the material in the extracellular space of neurons?
-beware-neurotoxins
-an optimal function of neurons
-many molecules could act as neurotransmitters, and we do not want accidental neurostimulation
3 boundary sites
-blood-brain barrier
-blood-CSF barrier
-meningeal barrier (blood-arachnoid barrier)
Capillaries are the smallest blood vessels. They are sites for what
exchange of material between blood and the surrounding area.
The structure of a generalized capillary:
pericytes: a cell/covering around the capillary
nucleus
endothelial cells
structure, location, and function
structure- endothelial cells joined by tight junctions
location:- skin, most nervous and connective tissue, and muscle tissue
function: least “leaky”—permit a narrow range of substances to cross the capillary walls
endothelial cells in continuous capillaries
The material does not really “leak” from the bloodstream between endothelial cells into the nervous tissue
Material moving from the bloodstream passes through the plasma membrane of the endothelial cells to get to nervous tissue
lipid-soluble molecules:
water-soluble molecules:
astrocytes and the tight junctions in the brain
capillaries limit the solutes that enter the brain ECF
Capillary of the brain vs normal capillary
-A typical capillary allows water and small solutes to move from the blood to the ECF– has no astrocytes
-Astrocytes and tight junctions in brain capillaries limit the solutes that enter the brain ECF–has astrocytes cover the cracks that would have allowed water and small solutes to pass through
what do astrocytes do for the capillaries of the brain
ASTROCYTES WRAP AROUND CAPILLARIES IN THE BRAIN.
They mediate the movement of materials between blood and neurons.
transporters of the plasma membrane and where are they facing
There are different transporters on the part of the plasma membrane facing the lumen of the capillary and the part of the plasma membrane facing the astrocytes.
pharmacist–if they want to make a drug for the brain–
need to make the drug so that it can cross the blood-brain barrier
Ependymal cells at choroid plexuses
—-Ependymal
Cells joined by tight junctions
—-Wastes and
unnecessary
solutes absorbed
—-CSF forms as a filtrate
containing glucose, oxygen,
vitamins, and ions
(Na+, Cl–, Mg2+, etc.)
—-The capillaries that bring blood to the choroid plexus are leaky.
* Material can easily move from blood stream between endothelial cells.
layers of the brain
Three layers of membranes known as meninges protect the brain and spinal cord (CNS). The delicate inner layer is the pia mater. The middle layer is the arachnoid, a web-like structure filled with fluid that cushions the brain. The tough outer layer is called the dura mater.
The subarachnoid space is below the arachnoid space and that is where the CSF is
