Chapter 10
Functions of Skeletal Muscle
* Movement of the skeleton
* Posture and body position
* Support of soft tissues
* Guard entrances and exits
* Maintain body temperature
* Storing nutrients
3 Layers of Connective Tissue
1. Epimysium – surrounds entire muscle
2. Perimysium – surrounds fascicles (muscle bundles)
3. Endomysium – surrounds individual muscle fibers
What Makes Up a Tendon?
Collagen fibers from epimysium, perimysium, and endomysium converge to form a tendon (or aponeurosis)
Characteristics of Skeletal Muscle
* Multinucleated
* Striated appearance
* Voluntary control
* Long cylindrical fibers
Myosatellite Cells
* Stem cells involved in muscle repair and regeneration
Sarcolemma
* Plasma membrane of a muscle fiber
Sarcoplasm
* Cytoplasm of muscle cell containing organelles, glycogen, and myoglobin
Sarcoplasmic Reticulum
* Modified ER that stores calcium ions (Ca²⁺)
* Releases Ca²⁺ to trigger contraction
Myofibrils
* Long protein bundles inside muscle fibers
* Responsible for contraction
* Composed of repeating units called **sarcomeres**
Myofilaments
Thin filaments: Actin, tropomyosin, troponin
Thick filaments: Myosin
Sarcomeres
* Functional unit of a myofibril
* From Z-line to Z-line
* Includes A band, I band, H zone, M line
Sliding Filament Theory
* Myosin heads bind to actin and pull, causing the sarcomere to shorten
* Requires Ca²⁺ and ATP
Acetylcholine (ACh)
* Neurotransmitter released at neuromuscular junction
* Triggers action potential in sarcolemma
Acetylcholinesterase (AChE)
* Enzyme that breaks down ACh in synaptic cleft to end stimulation
Steps That Initiate Contraction
1. ACh released at the neuromuscular junction
2. ACh binds to the ACh receptors on the sarcolemma
3. Gated channels open
4. Sodium ions rush into the cell generating an action potential inside the muscle cell
5. the action potential travels down the sarcolemma to the T tubules then to the triads
6. The action potential reaches the sarcoplasmic reticulum
7.Ca²⁺ binds to troponin → tropomyosin moves
8. The active sites on actin are exposed
9. Energized myosin heads (ATP-ADP+P) Bind to active sites on actin forming cross-bridges
10. Myosin heads pivot towards the M line (power stroke)- the bound ADP+P are released
11. ATP binds to myosin heads, breaking the bond between myosin and actin.
12. Myosin reactivation can occur when a free myosin head splits another ATP to ADP
Contraction Cycle
* Myosin binds → Power stroke → Detach (ATP required) → Reset
Rigor Mortis
* After death, ATP is depleted → myosin heads can’t detach → muscles stay contracted
Skeletal vs. Cardiac vs. Smooth Muscle
* Skeletal Muscle
* Voluntary control
* Striated (banded appearance)
* Long, cylindrical fibers
* Multinucleated
* Attached to bones
* Rapid, forceful contractions
* Cardiac Muscle
* Involuntary control
* Striated
* Branched cells with a single nucleus
* Connected by intercalated discs
* Found only in the heart
* Rhythmic, coordinated contractions
* Smooth Muscle
* Involuntary control
* Non-striated (smooth appearance)
* Spindle-shaped cells with a single nucleus
* Found in walls of hollow organs (e.g., intestines, blood vessels)
* Slow, sustained contractions
Key Diagrams
* Neuromuscular junction: a specialized synapse where a motor neuron communicates with a skeletal muscle fiber, enabling the nervous system to control muscle contraction
* Sarcomere structure: consisting of overlapping thin (actin) and thick (myosin) filaments arranged in a repeating pattern
Chapter 12: Nervous Tissue Review
Types of Cells in Nervous Tissue
Neurons – transmit impulses
Neuroglia (glial cells) – support and protect neurons
Anatomical Divisions
Central Nervous System (CNS) – brain + spinal cord
Peripheral Nervous System (PNS) – all neural tissue outside CNS
Functional Divisions
CNS – integration and processing
PNS – communication to/from CNS
* Afferent division – sensory input (to CNS)
* Efferent division– motor output (from CNS)
Efferent Subdivisions:
* Somatic Nervous System (SNS) – controls skeletal muscle (voluntary)
* Autonomic Nervous System (ANS) – regulates smooth/cardiac muscle, glands (involuntary)
Enteric Nervous System– digestive tract-specific, semi-autonomous
* Key Structures
Receptors – detect stimuli
Effectors – muscles/glands responding to stimuli
Neurons – functional units
Dendrites – receive input
Neuron Classifications
* Structural
Multipolar – most common in CNS
Unipolar – sensory neurons
Bipolar – special senses (retina, olfactory)
* Functional
Sensory (afferent)
Motor (efferent)
Interneurons – integration
Neuroglia
CNS: Astrocytes, oligodendrocytes, microglia, ependymal cells
PNS: Schwann cells, satellite cells
Membrane Potential Terms
Depolarization – membrane potential becomes more positive (Na⁺ in)
Repolarization – returns to resting potential (K⁺ out)
Hyperpolarization– membrane becomes more negative than resting
Signal Propagation
Continuous– unmyelinated axons (slow)
Saltatory – myelinated axons (fast, jumps node-to-node)
Fiber Types
Type A fibers: are the largest in diameter, heavily myelinated, and conduct nerve impulses the fastest. They are involved in somatic motor functions and carry sensory information such as touch, pressure, and proprioception.
Type B fibers: are smaller in diameter than Type A and are also myelinated, but conduct signals at a slower rate. These fibers are typically part of the autonomic nervous system, especially involved in transmitting signals to smooth muscle, cardiac muscle, and glands.
Type C fibers: are the smallest and unmyelinated, making them the slowest conducting fibers. They are associated with carrying slow pain, temperature, and autonomic control information.
Chapter 14
Major Brain Structures – Locations & Functions
Cerebrum: The largest part of the brain. It's responsible for higher brain functions like reasoning, memory, movement, and sensory processing. It's divided into left and right hemispheres.
Cerebellum: Located at the back of the brain, underneath the cerebrum. It coordinates movement, balance, and posture.
Gyri (gyrus): These are the raised ridges or folds on the surface of the brain. They increase the brain's surface area for more neural connections.
Sulci (sulcus): The grooves between gyri. Like gyri, they help increase surface area and divide brain regions.
Thalamus: Located deep in the brain, it acts as a relay station, directing sensory and motor signals to the cerebral cortex.
Hypothalamus: Just below the thalamus. It regulates body temperature, hunger, thirst, sleep, and hormones via the pituitary gland.
Midbrain: The top part of the brainstem. It processes visual and auditory info and helps control eye movement and reflexes.
Pons: Below the midbrain, it connects the brain to the cerebellum and assists in breathing and facial sensation.
Medulla Oblongata: The lowest part of the brainstem. It controls vital autonomic functions like breathing, heart rate, and blood pressure.
Brain Protections
Physical Protections:
* The skull acts as a hard barrier.
* The meninges (three layers: dura mater, arachnoid mater, and pia mater) surround and cushion the brain.
* Cerebrospinal fluid (CSF) circulates through the brain and spinal cord, providing cushioning and waste removal.
Chemical Protection:
* The blood-brain barrier keeps harmful substances in the blood from entering brain tissue, while allowing necessary nutrients through.
Disorders
Stroke: Occurs when blood flow to part of the brain is cut off, leading to cell death and potential loss of functions.
Ataxia: Lack of muscle control and coordination, typically caused by cerebellum damage.
Seizure: A sudden burst of abnormal electrical activity in the brain. Can cause convulsions, confusion, or loss of consciousness.
Other Key Brain Parts
Superior colliculi: Control visual reflexes, like tracking objects.
Inferior colliculi: Process auditory information.
Cerebral hemispheres are separated by the longitudinal fissure, and connected by the corpus callosum.
The cerebellar hemispheres are separated by the vermis, a narrow band of tissue.
Lobes and Cortices – Functions
Frontal lobe: Decision-making, voluntary movement, speech (Broca’s area), and personality.
Parietal lobe: Sensory perception and spatial reasoning.
Temporal lobe: Hearing, language understanding (Wernicke’s area), and memory.
Occipital lobe: Vision processing.
Motor cortex: Controls voluntary muscle movements (in frontal lobe).
Somatosensory cortex: Processes touch and body position (in parietal lobe).
Prefrontal cortex: Handles reasoning, planning, and behavior control.
Special Sensory Areas
Visual cortex: In the occipital lobe; processes vision.
Auditory cortex: In the temporal lobe; processes sound.
Olfactory cortex: At the base of the frontal and temporal lobes; processes smell.
Gustatory cortex: In the insula; processes taste.
Language Areas
Wernicke’s area: Found in the left temporal lobe; responsible for understanding language.
Broca’s area: In the left frontal lobe; responsible for producing speech.
Other Structures
Arbor vitae: “Tree of life” – the branching white matter inside the cerebellum.
Pineal gland: A small gland in the center of the brain that secretes melatonin and regulates the sleep-wake cycle.
Optic chiasm: Where the optic nerves from each eye cross to allow visual information from both eyes to be processed by both hemispheres.
Cranial Nerves – Key Ones
I (Olfactory): Smell.
II (Optic): Vision.
lll (Oculomotor): Controls eye movement, pupil constriction, and eyelid opening.
VII (Facial): Facial expressions, taste , tear and saliva production.
VIII (Vestibulocochlear): Hearing and balance.
X (Vagus): Controls heart rate, digestion, and other parasympathetic functions.