Different Nervous Systems And Muscloskeletal System Flashcards
MOTOR NERVOUS SYSTEM
• Provides voluntary movements of skeletal muscles
• Primary motor area located in precentral gyrus in control → motor cortex
• Basal nuclei initiate, stop, regulate conscious and subconscious contraction of skeletal muscles
• Cerebellum adjusts signals coming from motor cortex → smoothen and coordinate complex muscle contractions → fine motor skills, maintain balance, keep postare
The Corticospinal Tract
• 2 main motor tracts from primary motor area → spinal cord: lateral and anterior
• Primary motor area initiates voluntary movements → impulse through upper motor neurons → through brain stem → cross over to opposite side in medulla oblongata → spinal cord → synapse with lower motor neurons
• Lower motor neurons also extend from brain stem → skeletal muscles in head
MUSCLOSKELETAL SYSTEM
• Bones, muscles, joints, tendons, ligaments, and connective tissue
• Functions: produce heat and movements, maintain posture, stabilization, and store and move substances in the body
SKELETAL MUSCLES - Structure
• Muscle fibers contain myofibrils
• Sarcomeres = sections in myofibrils of actin and myosin (myofilaments) overlaping each other
• z-discs = seperate sarcomeres
• Zones in sarcomeres: A-bands = both filaments, I-bands = actin, H-zones = myosin
• Fibers packed into fascicles and surrounded by connective tissue
• Attached to bone by tendons (dense regular connective tissue extending beyond muscle)
Motor unit
• Motor neuron + muscle fibers it stimulates
• Stimulation of motor neuron → contraction af all muscle fibers in the motor unit
• Motor end plate = place where neuron and fiber meet → terminals approach the sacrolemma (cell membrane) of the muscle fiber
• Synaptic end bulb at end of terminal → vesicles with ACh (acetylcholine)
Neuro-muscular junction
• The synapse between synaptic end bulb and motor end plate
1. Impulse reach end bulb → trigger release of Ach → diffuse across synaptic cleft from motor neuron to motor and plate
2. ACh binds to receptors in motor and plate → muscle fiber depolarizes → Na+ channels open
3. Na+ flows in → muscle action potential → along sacrolemma and T-tubule (injunctions in membrane)
4. Sarcoplasmic reticulum close to T-tubule contain Ca2+ → action potential reach T-tubule → cast channels open in reticulum’s membrane → Ca2+ flow into sarcoplasm (cellplasm in muscle fiber)
Sliding filament mechanism
• Myosin pull actin towards center of sarcromere → sarcromere shortens → muscle fibers shortens → contraction
• Occurs if ATP is present and inflow of Ca2+ is enough
REFLEX
• A fast, involuntary sequence of actions in respons to a certain stimuli
• Called spinal reflex if integration in spinal cord; craniaI reflex if integration in brain stem
Reflex arc
• Definition: the pathway followed by nerve impulses causing a reflex
1. Sensory receptors get stimulated → generate one or more nerve impulses
2. Impulses conduct along sensory neuron axon → terminals located in a integrating center
3. sensory neuron synapse to a motor neuron (directIy or through one or more interneurons)
4. Impulses conduct along motor neuron → effector (=body part that will respond)
• Somatic reflex = skeletal muscle is the effector
• Automatic reflex = a gland, smooth or cardiac muscle are the effector
LONG BONE - structure
• Diaphysis (corpus) = the shaft
• Epiphysis = the ends
• Metaphysis = between shaft and ends, includes epiphyseal in growing bones
• Caput = the head, just at one end
• Collum = the neck, below head
• Condyle = the surface of the ends where next bone attaches
• Epicondyle = projection where tendons and ligaments attaches
LONG BONE - tissues
• Around bone = Compact bone
• Inside of epiphysis = Spongy bone
• Inside diaphysis = Medullary cavity
• Fat cells (adipocytes) storing energy in medullary cavity = yellow bone marrow
• In the spongy bone and produce blood cells = red bone marrow
• The condyles = articular cartilage
• Connective tissue surrounding the bone = Periosteum
BONES - Calcium homeostasis
• Bones reserv 99% of the body’s calcium
• Osteoclasts break down bones → Ca2+ out in the body
• Ostecytes also send out Ca2+ which usually is enough to maintain homeostasis
• Osteoblasts build bone with Ca2+ → calcium must be taken out of blood
• Parathyroid hormonet (PTH): blood Ca2+ levels decrease → receptor (PT cells) register → input: PTH synthesis speeds up → output: osteocytes and osteoclasts increase bone rerorption; kidneys retain Ca2+ in blood → kidneys produce calitriol which increase intestines absorption of Ca2+
• Calcitonin: produced in thyroid gland → inhibits osteoclasts → decreases Ca2+ levels in blood
BONES - hormones
• Sex hormones: stimulate osteoblasts → length growth (puberty) and strengthen bone (adulthood)
• Growth hormone (GH): stimulate osteoblasts and increase protein synthesis → general growth of body tissues (hGH) and normal bone growth
JOINTS - Structure
• Connective dense irregular/cartilage/bone tissue
• Synarthroses = immovable; ** Ampiarthoses** = slightly movable; Darthosis = freely movab le due to spaces between bones - synovial cavities
Synovial joints - diarthrosis
• Dense irregular connective tissue with synovial cavity
• Joint capsule surrounding joint: fibrous membrane = outer layer connecting to bone’s periosteum; synovial membrane = inner layer producing synovial fluid which fills the cavity
• Fluid provides nutrients and reduces friction by lubrication
• Ligaments restrict joint to move in wrong direction
SENSORY NERVOUS SYSTEM
• Provides sensation
• General senses → somatic and visceral
• Special senses → smell, taste, vision, hearing, balance
• Perception = primarily functions of cerebral cortex → the understanding of the sensation
Sensory receptors
• React to changes in energy = their stimuli
• Photoreceptors: light energy → vision
• Thermoreceptors: thermal energy → somatic senses
• Chemoreceptors: chemicals in body → smell, taste, somatic and visceral senses
• Mechanicreceptors: mechanical energy (deformation, stretching, bending of cells) → hearing, balence,somatic and visceral senses
Sensation - occurance
Change in energy → sensory receptor → electrical signal large enough to produce action potentials → conducted along neural tract to brain → region of brain must recieve rand integrate → impulse turned into sensation
Somatic senses
• Sensory receptors in skin, muscles, tendons, joints, and mucus membranes
• Sensory units = areas covered by one or several neurons with their receptors
• Types: tactile, thermal, propioceptive, and pain sensations
Somatic tactile sensation
• Encapsuleted (dendrites covered in connective tissue) mechanoreceptors → detect touch, pressure, and vibration
• Free nerve endings (just free dendrites) → detect itch and tickles
Somatic thermal sensation
• Warm receptors: in dermis
• Cold receptors: in epidemis
• Both thermoreceptors are free nerve endings
somatic, propriocaptive sensation
• Inform us of our body’s position
• Propriocaptors in muscloskeletal system inform us of muscle contraction, tension in tendons, and position of joints
• Propriocaptors in inner ear (hair cells) inform us of the head’s orientation
Pain sensation
• Nocireceptors = usually chemoreceptors reacting to chemicals released by damaged tissue
• Fast/acute pain → myelinated axons of nocireceptors, very precisely localized
• Slow/chronic pain → unmyelinated axons of nocireceptors, well localized but more diffuse and involves larger areas
SOMATIC SENSORY TRACTS
• Sending info from sensory receptors → primary somatosensory area in cerebral cortex = postcentral gyrus
• Spinal cord → medulla oblongata → mescencephalon → thalamas → postcentral gyrus
• 2 tracts: Posterior column - medial lemniscus pathway and Spinothalamatic pathway
Posterior (dorsal) column - medial lemniscus pathway
• For most tactile sensations - touch, pressure, and vibration - and for propriocaption
• Signal → spinal nerve → dorsal root → dorsal horn → medulla oblongata: 1st synapse from primary to secondary neuron in nuclei of medulla, switches side → mescencephalon through medial lemniscus → thalamus: 2nd synapse from secondary to tertiary neuron → postcentral gyrus
• Signals from left side of body → right side of postcentral gyrus (and the other way around)
Spinothalamatic pathway
• For pain and temperature, and some tactile sensation (itch and tickle)
• Signal → spinal nerve → dorsal root → dorsal horn: 1st synapse, switches side → medulla oblongata → mesencephalon → thalamus: 2nd synapse → postcentral gyrus
VISION (special sense)
• Structure: eyeball with 6 muscles, pupil with smooth muscle, iris conjunctiona, correa, lens, vitreous, retina with rods and cones (photoreceptors), central fovea and blind spot, optic nerve (2) and oculomotor nerve (3)
• Function:
- pupil can dialate or constrict → regulate intensity of incoming light
- lens refracts light → sharp image; convergence of eye when near vision → Neural accommodation
- photoreceptors convert light to action potentials
HEARING (special sense)
• Structure: Outer ear - ext. auditory canal and tympanic membrane; Middle ear - malleus, incus, stapes, and eustachian tube; Inner ear - chochlea, 3 semicircular canals, and vestibulocochlear nerve (8)
• Function: Sound waves → Tympanic membrane → mechanical movements → bones (malleus and incus) → Stapes vibrating in oval window → fluid pressure waves in Cochlea → mechanoreceptors signaling → vestibulocochlear nerve → auditory cortex
AUTONOMIC NERVOUS SYSTEM
• Autonomic sensory neurons → input to ANS, monitor internal conditions
• Autonomic motor neurons → output from ANS, regulate activities in affected tissues
• Autonomic motor pathway: 2 motor neurons connecting by autonomic ganglion
→ preganglionic neuron → ventral root → spinal nerve → ganglion → postganglionic neuron → tissue (smooth or cardiac muscle, or glands)
• 2 divisions: Sympathetic and Parasympathetic
Sympathetic system (ANS) - structure
• Synapse in Sympathetic trunk ganglia (rows at each side of spine) or prevertebral ganglia (in abdomen area)
• Preganglionic neurons leave CNS through spinal nerves at 12 thoracic segments and upper 2-3 lumbar segments, release acetylcholine at synapse
• Postganglionic neuron recieve acetylcholine with nicotinic receptors, and release noradrenaline to alpha or beta receptors at effector tissue
• smooth muscle in blood vessels: alpha → constrict; beta → dilate
Sympathetic system - effects
• Fright, flight, or fight
• Eyes → pupils dilate
• Blood → blood pressure increases and vessels dilate increasing blood flow through skeletal muscles, heart, and adipose (fat) tissue
• Heart → rate and force increase
• Airways → dilate → more air → better gas exchange in blood
• Digestive and urinary systems → blood flow and activity decrease
Parasympathetic system (ANS) - structure
• Ganglions are located in the head or target organs and preganglionic synapse with few postganglionic neurons (opposite in sympathetic)
• Preganglionic neurons leave CNS via 4 cranial nerves (3, 7, 9, 10) or 2-4 sacral segments, release acetylcholine at synapse
• Postganglionic neurons recieve acetylcholine with nicotinic receptors and release acetylcholine to muscarinic receptors at effector tissue
Parasympathetic system - effects
• Rest and digest
• Eyes → pupils constrict
• Heart → rate decreases
• Airways → constrict
• Digestive and urinary systems → activity and blood flow increases
Adrenal medulla
• Inside adrenal glands
• A modified sympathetic ganglion with cells that lack axons → preganglionic neurons stimulate adrenal medulla to release hormones instead → adrenaline and noradrenaline
