How is touch perceived?
- Location of a stimulus
- Intensity of touch: signaled by frequency of action potentials conducted, the more intense the touch the more action potentials sent
types of cutaneous mechanoreceptors and how they work
merkel disk:
- located in the lowest layer of the epidermis
- exhibit slow adaptation and respond to steady pressure.
meissner corpuscles:
- mediates the sensation of light touch.
- concentrated in areas sensitive to light touch, such as fingertips, lips, and nipples.
- capsule surrounding the ending of a sensory nerve (or nerves) that wind between stacks of flattened Schwann cells in the capsule interior.
- Schwann cells dissipate deformation of the nerve endings
How do neurons communicate with each other?
- Chemical signaling: caused by depolarization creating an action potential which is then transmittedfrom one neuron to another until it gets to CNS.
Evaluate how osteopathic physicians use touch in the care of patients
Osteopathic physicians use touch mainly to diagnose and evaluate. However their touch can show compassion and give patients self worth as long as it is done in caring and respectful way.
Nerve pathway that connect the cutaneous mechanoreceptors with the primary sensory area of the cerebral cortex
- First order: Afferent fiber to cell body in dorsal root ganglia in peripheral nerve
- Second order: From dorsal root ganglia to medulla oblongata
- Third order: From medulla oblongata crosses over via medial lamniscus and up to thalamus/ primary somatosensory cortex in parietal lobe
region of the brain whose neurons must be stimulated for conscious perception of touch
- somatosensory cortex, specifically the postcentral gyrus of parietal lobe
- it is represented by the homunculus
types of receptors for neurotransmitters (2)
- ligand gated ion channel (ionotropic): action potential is carried out quickly (nicotinic)
- linked to intracellular second messengers (metabotropic) action potential takes long time (muscarinic, adrenergic)
Absolute refractory period
- amount of time from when first stimulus is given until the start of repolarization
- during this time the cell has hit its threshold, depolarized, hit peak voltage, and begun to repolarize by closing inactivation gates. The gates must be closed before channels can be reopened
Relative refractory period
time after absolute refractory period when another impulse can be started but only if the stimulus is stronger due to the cell continuing to repolarize by pumping out K (it has not fully reached its resting negative voltage- so the outside of the cell would have to be extremely positive in order to offset the voltage inside the cell to make the inside to feel negative)
How do K and Na cause action potential
- Phases of action potential are due to changes in membrane Na and K conductance within a certain time
- Once threshold voltage is exceeded, voltage gated Na channels opened which causes rapid depolarization
- Leads to peak voltage being hit-depolarization stops and repolarization starts by closing Na channels and opening K channels (K flows out of cell)
- Afterhyperpolarization will occur if K continues to be released even after cell hits normal resting voltage concentration (normal negative amount)
resting membrane potential
voltage difference across a cell membrane when the cell is at rest. Inside of cell is negative and outside of cell is positive
Shapes of muscle (7)
- flat : parallel fibers often with aponeurosis (flat sheet of tendon used to anchor muscle to skeleton),
- pennate: feather-like in arrangement of fascicles and may be uni, bi, or multi
- Fusiform: spindle shapes with round, thick belly and tapered ends
- convergent: arise from broad area and converge to single tendon
- quadrate: have four equal sides
- circular or sphincteral: surround body opening or orifice, constricting when contracted
- multiheaded/multibellied: have more than one head of attachment or more than one contractile belly
Diff types of muscles (3)
- skeletal striated muscle: voluntary, somatic muscle makes up gross skeletal muscles that compose the muscular system, moving, or stabilizing bones and other structures.
- Cardiac striated muscle: involuntary visceral muscle that forms most of the walls of the heart and adjacent parts of the great vessels, such as the aorta, and pumps blood.
- Smooth muscle: involuntary, visceral muscle that forms part of the walls of most vessels and hollow organs, moves substances through them by coordinated sequential contractions
Types of muscle contraction(3)
- Reflexive: occur unconsciously; ex. Diaphragm moving to levels of oxygen and carbon dioxide to aid in respiration
- Tonic: muscles always slightly contracted to give muscle firmness, which assists stability of joints and maintains posture
- Phasic:
- Isotonic: muscle changes length in relationship to production of movement
- Concentric: muscle shortens with contraction; used by main muscle
- Eccentric: muscle lengthen with contraction; controlled and gradual relaxation; used by antagonist muscle
- Isometric: muscles does not change length and no movement occurs but there is more force than tonic contraction to resist gravity/antagonistic force
Types of joints (3)
- Synovial
- Fibrous
- Catilaginous
Functions of Muscles (4):
- Prime mover: main muscle responsible for producing desired movement and doing most of energy required
- Fixator: Steadies proximal parts of limb through isometric contraction while movements are occurring in distal parts
- Synergist: Complements action of prime mover. May directly assist a prime mover providing weaker/less mechanically advantaged component of same movement OR assist indirectly by serving of fixator of intervening joint when muscle passes over more than one joint. Can have multiple synergists.
- Antagonist: muscle that opposes the action of another muscle , primary antagonist opposes the prime mover, but synergists may also be opposed by secondary antagonists
Processes for formation of bone
- Intramembranous: mesenchymal model of bones form during embryonic period, direct ossification of mesenchyme
- Endochondral ossification: cartilage model of bones form during embryonic stage, mesenchyme differentiates into chondroblasts forming cartilage. The mid region of the bone calcifies and periosteal capillaries grow into the calcified cartilage to form a periosteal bud. The periosteal bud is the primary ossification center because the bone it grows replaces the cartilage in the mid region of the bone (diaphysis).
Differences between the long bone features of a child and adult in terms of the growth plates.
- child: more cartilage due to growth plates. As the child develops into an adult growth plates are shortened as the cartilage is replaced by bones.
- The adult bone does not have any cartilage left in the growth plate due to the primary and secondary ossification centers fusing.
Somatosensory communication
- pressure is applied onto a sensory nerve which allows for influx of Na which causes depolarization and begins a generator potential.
- generator potential creates a current through the axon membrane to the impulse initiation region where an action potential is created.
- action potential influx of Ca into presynaptic cell which then signals for neurotransmitters to be released into synaptic cleft
- neurotransmitters bind to postsynaptic neuron and continue the action potential continues with influx of Ca2 into next nerve
Synovial
a. Bones united by joint capsule which encloses the joint
b. Bones have cartilage on articulating ends allowing for smooth movement, rest of cavity is filled with synovial fluid and the internal aspects are covered with synovial membrane
c. Allow for lots of movement and are reinforced by separate ligaments or thickening of portion of joint capsule
Fibrous
a. Bones are united by fibrous tissue
b. Movement of joint depends on how long fibers of joint are
- Syndesmosis: unites bones with sheet of fibrous tissues, no movement, bones in skull
- Dento-alveolar syndesmosis: unites bones that forms peg fitting into hole (tooth), allows for some movement, but too much movement is usually caused by pathological state
Cartilaginous
Bones united by cartilage
- Primary: Uses hyaline cartilage; permits slight bending during early life, used for temporary union, particularly to permit bone to grow until it eventually is converted into bone
- Secondary: Uses fibrocartilage to form strong, slightly flexible joints; can be seen in intervertebral discs which allow for disc to be strong yet absorb shock and be flexible to bending.
