Nervous 2 Flashcards
(52 cards)
Nerve Pathways: Pyramidal:
Pyramidal:
Lateral tract
AKA UPPER MOTOR NEURONS
Disorders Characterized by: babinski, hypertonic spasticity, clonus (test at ankle), hyperreflexia, loss of fine motor skills, muscle wasting
Impulses downward through the spinal cord. By means of direct routes and interconnecting neurons in the cord, these nerves eventually excite the alpha motor neurons that control/modulate the fine and gross properties of skeletal muscles during all purposeful movements.
Nerve Pathways: Extrapyramidal:
Extrapyramidal:
Ventromedial tract
AKA LOWER MOTOR NEURONS
Disorders Characterized by: Parkinsonism OR dyskinesias.
Neurons in this tract originate in the brainstem and connect at all levels of the spinal cord. They control posture and provide a continual background level of neuromuscular tone. (Involuntary movements- Balance/Posture)
Reflex Arc
Reflex Arc:
Stimulus
Peripheral receptor
Afferent sensory fiber
Interneuron in spinal cord
Efferent motor fiber
Effector
Afferent neurons enter the spinal cord through the dorsal root
Transmit sensory input from peripheral receptors
Interneurons relay info to different levels of the cord.
Impulses then pass over the motor (efferent) pathway to the effector organ
Dyskinesias
Extra-pyramidal disorder. Dyskinesias
Dyskinesias
patient may make twitching or rolling motions. She cannot control the movements and usually is incapable of sitting still
Tremor
Extra-pyramidal disorder. Dyskinesias
Tremor
Rest tremor occurs when the affected body part is completely supported against gravity.
Action tremors are produced by voluntary muscle contraction.
postural, isometric, kinetic tremors.
Chorea
Extra-pyramidal disorder. Dyskinesias
Chorea
Brief, irregular movements that are not repetitive or rhymic, but appear to flow from one muscle to the next
Myocolonus
Extra-pyramidal disorder. Dyskinesias
Myocolonus
Is continuous flow of involuntary irregular movement. The movements are rapid, jerky, non rhythmic and explosive that flit from portion of the body to another in random sequence.
Tics
Extra-pyramidal disorder. Dyskinesias
Tics
Repetitive, stereotyped, semipurposeful movement.
Patient could willingly suppress them at expense of mounting inner tension
Dystonia
Extra-pyramidal disorder. Dyskinesias
Dystonia
relate to involuntary and abnormal muscle tension that forces patients into awkward and sometimes painful twisted or bent positions.
Akinetic rigid syndrome
Parkinsons. Extra-pyramidal disorder.
The Babinski Sign
The normal response in an adult to stroking the sole of the foot is flexion of the big toe, and often the other toes. Following damage to descending upper motor neuron pathways, however, this stimulus elicits extension of the big toe and a fanning of the other toes.
What is Clonus and how to test it?
oscillatory motor response to muscle stretching
Positive when stretching calf with (via hand on foot) and foot starts shaking in response
Motor unit:
Motor pool:
Motor unit: made of 1 alpha motor neuron + muscle fibers
Motor pool: all alpha motor neurons projecting to a given muscle
Size Principle:
Type 1 fiber
Type 2 fiber
Size Principle: Start small. AKA fast-twitch is recruited last.
Type 1 fiber = slow twitch = endurance, aka red muscles.
Type 2 fiber = fast twitch = power, aka white muscles.
What is the basic functional unit of a muscle fiber?
Sarcomere
Myocyte
Myofibril
Sarcomere
A myocyte is a muscle fiber
A myofibril is a bundle of sarcomeres
Muscle spindles
Outside: Extrafusal fibers
Inside: Intrafusal fibers
Nuclear bag (like a bag in the center)
Nuclear chain (along the fiber like chains)
Innervated by gamma-motor neurons, which change the spindle’s length.
Around intrafusal fibers
Primary spindle afferents (1a):
Secondary spindle afferents (2):
Around intrafusal fibers
Primary spindle afferents (1a): annulospiral, dynamic changes in length (tapping and vibration)
Secondary spindle afferents (2): flower-spray, static changes in length (posture)
Stretching of the intrafusals:
2 ways
Activating gamma motor neurons, shortening ends, stretching center.
Passively lengthening or shortening of intrafusal fibers
Muscle contraction process
- Excitatory Post Synaptic Potential (EPSP) reaches muscle fibril and AP propagates.
- Sarcolemma release Ca++
- Ca++ binding to TROPONIN exposes binding site.
- Muscle contraction first begins with cross-bridging of actin and myosin.
- ATP is currently bound to myosin
- Release of ATP (ADP and Pi) => POWER STROKE
- New ATP joining = BREAKING CROSS BRIDGE
- Hydrolyzing the ATP => myosin bends again into “cocked”
The first step in the process of a muscle contraction is for Ca++ to bind to _______ so that _________ can slide away from the binding sites on the actin strands.
Troponin, tropomyosin
During the cross-bridge cycle, when is myosin in a high-energy configuration?
Before the power stroke
After the power stroke
Before the power stroke.
This energy is expended as the myosin head moves through the power stroke, and at the end of the power stroke, the myosin head is in a low-energy position. After the power stroke, ADP is released; however, the formed cross-bridge is still in place, and actin and myosin are bound together. As long as ATP is available, it readily attaches to myosin, the cross-bridge cycle can recur, and muscle contraction can continue
Muscle Soreness caused by:
- Minute tears in muscle tissue
- Osmotic pressure changes causing edema around muscle.
- Muscle spasms
- Overstretching/tearing of muscle harness
- Acute inflammation (the later part of working out)
- Alteration in calcium regulation
Notable: lactic acid only causes initial soreness in working out. (30 mins after)
A person runs a 10K and is sore several days afterwards. Is lactic acid the culprit?
No! The soreness is caused by microtears in the muscle tissue and possibly inflammation
Labeled Line Principle
nerve fibers only transmit a single modality of sensation (i.e. crushing and burning both cause pain)
