Muscle Physiology Muscle physiology

Motor pathways Spinal tracts Basal ganglia circuitry Pon and cerebellum

Extra-pyramidal tracts Segmental Mechanisms- a Cerebral Cortex Motor Areas (6/4/8) Somatosensory Areas (3a/3b/1/2/5/7) Extra-pyramidal tracts Feedback loop Thalamus VA/VL Basal Ganglia Cerebellum Pyramidal tract Brainstem Pathways RN RF VN Medial Lateral Segmental Mechanisms- a Muscles

Efferent motor commands starting from the cerebral cortex are contralateral (crossed), meaning that the left cortex controls the muscles on the right side of the body (and vice versa), whereas motor commands starting from the brainstem influences ipsilateral (same side) motor activity. 모든 감각정보는 thalamus를 지나지만 이 부분은 베이설 갱길리아 부분은 포함되지 않아. 오른쪽 스파이널 코드로 들어가는 부분 브레인 스템에서 시작되는 부분은 크로스오버가 일어나지 않고 입실론쪽으로 들어가게 됨 이 사진은 간단한 예만 표시. 들어가는 에이프런, Efferent 코텍스에서 나가는 모토 반응은 스리브럴 코텍스에서 시작되는 크로스오버되는데 이건 왼쪽 코텍스에서 시작되는 모터리스판스는 반대쪽 머슬을 컨트롤. 그러나 브레인스템에서 시작하는 모토 반응은(command는 뇌에서 반응 명령을 내리는 것을 표현하기 위한 단어)

Extensive neural networks between the major “motor areas” of the cerebral cortex permit fine control of movement, utilizing sensory and intentional signals to activate the appropriate motor neurons at an appropriate level of stimulation. Primary motor는 가장 중요한을 의미. 센스 인포메이션과 모터인포메이션은 서로 연결되. 색깔 칠해진 모든 부분이 모터 코텍스 4 6 8반응은 프라이머리 모터 코텍스와 관련된 반응 B 그림에 있는 것들은 스파이널로 가서 여러 가정을 거치거나 안거치거나. 그래서 피라미드 pathway라고 명명 브레인스템에서 시작하는 것은 교차 없이 진행

Somatotopic map The location and relative size of the cartoon body- shapes represent the location and relative number of motor-related neurons in the cerebral cortex.

Altered processing abilities in the neural components regulating motor commands can cause motor problems, such as Parkinson’s disease. 모터페스웨이들이 망가지게 되면 운동장애가 와 – 파킨슨. 모터 패스웨이 특히 베이설 뉴클레이 파괴가 파킨슨의 주요 원인. 씨엔에스 뉴런은 다시 재생이 안됨. 이것이 망가지는 경우는 2가지 - 이상한 물질이 생겨 or 충격에 의해서 pathways가 끊어지는 경우(1차적 원인) 뉴런이 아닌 물질에서 무엇이 생겨서 영향을 미치는 경우 등 으로 인해 뇌기능이 없. 모터, 센서리, 센세이션 기능들이 떨어지게 되. 따라서 뇌의 변화를 배터리로 비유. 알크하이머는 아세틸콜린 뉴런이 우리 뇌 대표적인데 이것에 문제가 생겨 인지기능에 장애가 생김. -

form command relay command execute command

Acting on both local reflex circuits and relaying impulses to the brain, muscle spindles and Golgi tendon organs provide information about muscle position and stretch in order to finely regulate the speed and intensity of muscle contraction: sensing the degree for stretching muscle fibers and tendons in skeletal muscle. 머슬(말단기관)에서 뇌로 정보를 전달하는 방식에 대한 내용 보행수단이자 여러 운동기능을 하는 머슬의 상태를 감지하고 어떻게 명령이 하달되는지 로컬 리플렉스는 뇌로 가지 않고 실행기관으로 바로 가는 것을 가리키는 말. 돌에 찧ㅇㅆ는 지 불에 데였는지 아는 정보 전달은 뇌로 진행됨. 뼈에붙은 근육이 늘어난 정도, 위치 정보를 전달. 다른 엑스트라 머슬들의 변화를 유도하기 위해서. -

뼈에 붙은 것을 tendon이라고 함. 일반적인 세포 형태가 아니야. 이 세포는 다른 기능은 필요없. 띤 필라멘트만 거의 대부분 존재하게 되. 근육 이완 상태를 전달해주는 신경들이 존재해. 이 신경은 모터뉴런이 아님. 여기에는 모터뉴런이 따로 존재해서 여기에 달라붙어있어 이 그림에는 없. 여기 뉴런은 cns에 정보를 전달하는 것으로 스파이널코드로 넘어간다.뼈와 붙어있는 golgi tendon organ이 있고 안쪽에 말려 있는 것은 형태에 따라서 스핀들이라는 이름을 붙였어. 이 안쪽에도 인트라퓨설 머슬 파이버가 있어. 이 바깥쪽에 머슬파이버가 있어 근수축하는 것은 스트레치 리셉터가 담당하는데 뼈와 있는 근육은 씨엔에스로 연결

Regardless of the reason for a change in length, the stretched spindle in scenario (a) generates a burst of action potentials as the muscle is lengthened; in scenario (b), the shortened spindle produces fewer action potentials from the spindle. A 상황에서는 근육이 늘어나. 그럴 경우 안쪽 머슬스핀들에 있는 센스리셉터가 cns로 보내 얘들이 늘어나는 정보가 엑션 포텐셜 파이어링을 증가하는 방식으로 활동 수축하게 되면 엑션포텐셜파이어링이 줄어들어. 이런 두 가지 방식으로

1) compensatory contraction in extensor muscles. Tapping the patellar tendon lengthens the stretch receptor in the associated extensor muscle in the thigh. Responses include: 1) compensatory contraction in extensor muscles. 2) relaxation in the opposing flexor. 3) sensory afferent delivery to the brain. 여러 곳에 포진한 근육들이 각기 어떻게 조절되는지를 . 무릎을 두드렸을 때 허벅지 바깥쪽 근육과 안쪽 근육이 서로 상반된 활동을 해.

A에서는 엑션포텐셜이 증가하면서 다리로 내려와 아세틸콜린을 분비, 수축이 일어남 C에서는 다른쪽 다리 B에서는 뉴런 억제 반응. 반대쪽 플렉서 머슬은 이완이 되. 릴렉세이션이 됨.

Activation of Golgi tendon organs Activation of Golgi tendon organs. When a muscle is contracting, stretch of the tendon produces more action potentials in afferent neurons (right), increasing reflex and sensory relay to the brain 윗장에서는 중간에 볼록하게 올라온 근육 이야기. 골지텐더는 중간 근육에 따라 늘어나게 되는데 그 늘어난 정도 정보가 cns에 전달

Contraction of the extensor muscle on the thigh tenses the Golgi tendon organ and activates it to fire action potentials. Responses include: Inhibition of the motor neurons that innervate to the extensor muscle (A) Excitation in the opposing flexor’s motor neurons (B).

골지텐더와 관련된 뉴런은, a와 b 두종류. 이 상황에서는 a에서 억제. 아세틸콜린이 나오지 않아서 이완이 됨.

1 2 3 Pain sensory afferents detect pain in foot and The neural components of the pain-withdrawal reflex Pain sensory afferents detect pain in foot and send action potentials to the dorsal horn of spinal cord. Interneurons in the spinal cord activate flexor muscles on the “pained” side of the body and extensor muscles on the opposite side of the body. Muscles move body away from painful stimulus. 1 2 Could alter to show 1, 2, 3 in sequence 압정을 밟았을 때 즉 페인과 관련한 모터 반응 이런 것은 스파이널에서 이루어짐 페인리셉터에서 탈분극이 일어나서 3

Muscle contraction

Key concepts The sliding filament mechanism, in which myosin filaments bind to and move actin filaments, is the basis for shortening of stimulated skeletal, smooth, and cardiac muscles. In all three types of muscle, myosin and actin interactions are regulated by the availability of Ca2+ ions. Changes in the membrane potential of muscles are linked to internal changes in Ca2+ release. Smooth muscles operate in a wide variety of involuntary functions such as regulation of blood pressure and movement of materials in the gut.

Skeletal muscle

Characteristics of muscle fibers

Myosin’s cross-bridges of thick filament bind to actin Myosin’s cross-bridges of thick filament bind to actin. The cross-bridges then flex to slide actins, reducing the width of the I-band and H-zone, but not A-band.

Myosin is actually a polymer of myosin molecules, each of which has a flexible cross-bridge that binds ATP and actin of thin filament.

In relaxed skeletal muscle, tropomyosin blocks the cross-bridge binding site on actin. Contraction occurs when Ca2+ binds to troponin; this complex then pulls tropomyosin away from the cross-bridge binding site.

The cross-bridge cycle requires ATP

A. Optimal-length sarcomere: lots of actin-myosin overlap and plenty of room to slide. A. B. B. Short sarcomere: actin filaments lack room to slide, so little tension can be developed. C. C. Long sarcomere: actin and myosin do not overlap much, so little tension can be developed.

In skeletal muscle, ATP production via substrate phosphorylation is supplemented by the availability of creatine phosphate. Skeletal muscle’s capacity to produce ATP via oxidative phosphorylation is further supplemented by the availability of molecular oxygen bound to intracellular myoglobin, fatty acids, and proteins.

Motor unit is the connection of somatic motor neuron and skeletal muscle. A motor neuron innervates to all of the muscle fibers by collateral axon terminals. 파이버들 하나하나에 모두 다 뉴런이 연결되는 건 아니고 거의 다 와서 분지가 되는 형태야. 이 분지된 것들이 동시다발적으로 파이버드이 같이 움직일 수 있도록 분지뉴런이 다 달라 붙음. -

Mechanism for muscle contraction 1. The neuromuscular junction is the point of synaptic contact between the axon terminal of a motor neuron and the muscle fiber. Action potentials arrived in the motor neuron cause acetylcholine (ACh) release into the synaptic cleft. 2. On the membrane of the muscle fiber, the receptors for Ach respond to its binding by increasing Na+ entry into the fiber, causing a graded depolarization (end plate potential, EPP). 3. The EPP typically exceeds threshold for the nearby voltage-gate Na+ channels, so an action potential occurs on the muscle fiber.

이 지역에서 아세틸콜린의 역할은 – 근수축 End plate = graded plate 근세포에서도 신호전달이 일어나고 그게 근수축을 일으켜

The transverse (T) tubules bring action potentials into the interior of the skeletal muscle fibers, so that the wave of depolarization passes close to the SR, stimulating the release of Ca2+.

Passage of an action potential along the T- tubule opens nearby the voltage-gated Ca2+ channels, called “ryanodine receptor,” located on the SR. Released Ca2+ readily diffuse into all of the troponin (calcium binding) sites. The calcium-troponin complex “pulls” tropomyosin off the myosin-binding site of actin, thus allowing the binding of the cross-bridge, followed by its flexing to slide the actin filament.

DHP: dihydropyridine, voltage sensor

The latent period between excitation and development of tension in a skeletal muscle includes the time needed to release Ca2+ from the SR, move tropomyosin, and cycle the cross-bridges.

Isometric contraction iso = same; tonic = tension; metric = length Isometric contraction When a muscle develops tension but does not shorten. Tension increases rapidly and dissipates slowly Isotonic contraction Muscle shortens, while the load on the muscle remains constant. Shortening occurs slowly, only after taking up elastic tension; the relaxing muscle quickly returns to its resting length. 수축까지의 이야기를 했음 장력 이야기 – 1. isometric – 텐션 수축은 만드는데 짧아지지는 않아. 들 수 없는 테이블을 들려 할 때 슬로우하기 ㅏ사라져 2. Isotonic contraction – 머셀은 짧아지지만

All three are isotonic contractions. Iceload Light loads are more rapidly moved than heavy loads.

Temporal summation Complete dissipation of elastic tension between subsequent stimuli. S3 occurred prior to the complete dissipation of elastic tension from S2. S3 occurred prior to the dissipation of ANY elastic tension from S2.

partial dissipation of elastic tension between subsequent stimuli. Tetanus, a maintained contraction in response to repeated stimulation Unfused tetanus: partial dissipation of elastic tension between subsequent stimuli. Fused tetanus: no time for dissipation of elastic tension between rapidly recurring stimuli. The mechanical response of a single muscle fiber to a single action potential. 10/sec 100/sec

repetitive (repeated) stimulation leads to fatigue, evident as In skeletal muscle, repetitive (repeated) stimulation leads to fatigue, evident as reduced tension. Rest overcomes fatigue, but fatigue will reoccur sooner if inadequate recovery time passes: time-dependent. decline in muscle tension as a results of previous contractile activity

Most skeletal muscles include all three types. Motor unit 1. Slow-oxidative skeletal muscle responds well to repetitive stimulation without becoming fatigued; muscles of body posture are examples. Motor unit 2. Fast-oxidative skeletal muscle responds quickly and to repetitive stimulation without becoming fatigued; muscles used in walking are examples. Motor unit 3. Fast-glycolytic skeletal muscle is used for quick bursts of strong activation, such as muscles used to jump or to run a short sprint. 인체의 구조는 다 달라 따라서 근욱이 모습도 다ㅑ= 2. 반복적인

the greatest rise in the tetanic muscle tension Motor unit 3 produces the greatest rise in the tetanic muscle tension because it is composed of the largest-diameter fibers and contains the largest number of fibers per motor unit. Fast-oxidative

Note: Because fast-glycolytic fibers have significant glycolytic capacity, they are sometimes called “fast oxidative-glycolytic [FOG] fibers.

sets to refine movement, How can gastrocnemius contraction result in two different movements? Flexors and extensors work in antagonistic sets to refine movement, and to allow force generation in two opposite directions.

Muscle contraction must generate 70 kg force to hold a 10 kg object that is 30 cm away from the site of muscle attachment.

The level system of the arm amplifies the velocity of the biceps muscle, producing a greater velocity of the hand. The range of movement is also amplified (1 cm of shortening by muscle produces 7 cm of movement by the hand).

Thick and thin filaments, biochemically similar to those in skeletal muscle fibers, interact to cause smooth muscle contraction. In smooth muscle, Ca2+-CaM complex binds to MLCK (myosin light-chain kinase), which phosphorylates myosin cross bridges. 심장근, 골격근이랑 좀 달라. 필라멘트는 같은데

Rhythmic changes in the membrane potential of smooth muscles result in the rhythmic patterns of action potentials and therefore rhythmic contractions in the gut. Neighboring cells use gap junctions to further coordinate these rhythmic contractions. An AP prior to the main AP