Cell Types, Skeletal, Muscular, Nervous Systems

• Notes cover generalized vs specialized cells, skeletal system, muscle system, nervous system, and special senses

Generalized Cells vs. Specialized Cells

• Generalized cells serve as a basic cell model
• Specialized cells have unique structures for specific functions and modified organelles

Generalized Cell Structure

• Possess a nucleus, cytoplasm, and plasma membrane
• Contain basic organelles for general cell functions
• Are simple and not adapted for specific function

Generalized Cell Function

• Carry out fundamental life processes like metabolism, growth, and reproduction
• Do not perform highly specific functions

Specialized Cell Structure

• Have unique shapes and structures adapted for specific functions.
• Contain modified organelles to perform specialized tasks
• Nerve cells have long extensions for signal transmission
• Muscle cells contain contractile fibers

Specialized Cell Function

• Perform specific tasks in the body
• Work together to maintain homeostasis

Examples of Specialized Cells

• Red blood cells transport oxygen using hemoglobin
• Neurons transmit electrical signals
• Muscle cells contract to produce movement
• Epithelial cells form protective barriers

Skeletal System

• Divided into the axial and appendicular skeleton

Axial Skeleton

• Includes the skull, vertebral column, and rib cage

Appendicular Skeleton

• Includes the shoulder girdle, upper limbs, pelvic girdle, and lower limbs

Upper Skeleton (Appendicular)

• Includes the shoulder girdle and upper limbs to allow movement and manipulation

Shoulder Girdle (Pectoral Girdle)

• Clavicle connects the arm to the axial skeleton and provides support
• Scapula is a triangular bone with multiple muscle attachment points

Upper Limb (Arm and Forearm)

• Humerus is the largest upper limb bone that connects to the scapula
• Radius rotates around the ulna and is involved in wrist movement
• Ulna is longer than the radius and forms the elbow joint with the humerus

Hand (Wrist, Palm, and Fingers)

• Carpals are eight wrist bones in two rows: scaphoid, lunate, triquetrum, pisiform, trapezium, trapezoid, capitate, and hamate
• Metacarpals are five bones that form the structure of the palm
• Phalanges include 14 finger bones with each finger having 3 bones except the thumb, which has 2

Lower Skeleton (Appendicular)

• Supports weight, balance, and movement

Pelvic Girdle (Hip Bones)

• Ilium is the large, flared upper part of the hip bone
• Ischium is the lower, back portion supporting body weight when sitting
• Pubis is the front part of the pelvis, forming the pubic symphysis

Lower Limb (Thigh, Leg, and Foot)

• Femur is the longest, strongest bone that connects the pelvis at the hip
• Patella protects the knee joint
• Tibia is the larger, weight-bearing lower leg bone forming the knee joint with the femur
• Fibula is a slender bone for muscle attachment that does not bear weight

Foot (Ankle, Sole, and Toes)

• Tarsals consist of seven ankle bones including the Calcaneus (heel bone) and Talus (connects foot to tibia/fibula)
• Metatarsals consist of five foot bones forming the sole
• Phalanges consist of 14 toe bones arranged similarly to fingers

Bone Classification

• Based on shape and function

Long Bones

• Longer than wide, contain mostly compact bone with spongy bone at ends
• Support weight and facilitate movement
• Examples include the femur, humerus, radius, ulna, tibia, fibula, metacarpals, metatarsals, and phalanges

Short Bones

• Cube-shaped, mostly spongy bone with an outer layer of compact bone
• Provide stability and support with limited movement
• Examples include carpals and tarsals

Flat Bones

• Thin, flattened, usually curved, with layers of compact bone sandwiching spongy bone
• Protect internal organs and provide attachment points for muscles
• Examples include skull bones, ribs, sternum, and scapula

Irregular Bones

• Complex shapes that do not fit into other categories
• Provide protection, support, and flexibility
• Examples include vertebrae, hip bones, sacrum, and mandible

Sesamoid Bones

• Small, round bones embedded within tendons
• Reduce friction and modify pressure on tendons
• Example is patella (kneecap)

Bone Composition and Structure

• Compact Bone: Dense, smooth, and forms the outer layer
• Spongy Bone: Porous, contains red marrow and is in epiphyses of long bones
• Periosteum: Outer fibrous covering with nerves and blood vessels
• Medullary Cavity: Hollow space inside long bones containing yellow marrow (fat storage)
• Epiphyseal Plate: Cartilage area in growing bones; it converts to the epiphyseal line in adults

Bone Functions

• Support: Provides body structure and shape
• Protection: Shields vital organs
• Movement: Works with muscles for locomotion
• Mineral Storage: Stores calcium and phosphorus
• Blood Cell Formation (Hematopoiesis): Red marrow produces blood cells

Skeletal System Conclusion

• The upper skeletal system allows movement and dexterity
• The lower skeletal system allows weight-bearing and stability
• Bones are classified into long, short, flat, irregular, and sesamoid, each with unique functions
• The skeletal system gives support, protection, movement, mineral storage, and blood cell production

Muscular System

Major Muscles of the Body and Their Functions

Head and Neck Muscles

• Frontalis: Raises eyebrows and wrinkles forehead
• Orbicularis Oculi: Closes eyelids
• Orbicularis Oris: Controls lip movements
• Zygomaticus: Raises corners of the mouth
• Masseter: Closes jaw for chewing
• Temporalis: Assists in chewing
• Sternocleidomastoid: Rotates and flexes the head
• Trapezius: Moves the shoulder and extends the neck

Trunk and Shoulder Muscles

• Pectoralis Major: Moves the shoulder joint, flexes, and adducts arm
• Rectus Abdominis: Flexes the vertebral column and compresses abdomen
• External and Internal Obliques: Rotate and flex the torso
• Latissimus Dorsi: Extends and adducts the arm
• Deltoid: Abducts the arm and aids in shoulder movement

Arm and Forearm Muscles

• Biceps Brachii: Flexes the elbow and supinates forearm
• Triceps Brachii: Extends the elbow
• Brachialis: Assists biceps in flexing the elbow
• Brachioradialis: Helps with forearm flexion
• Flexor Carpi Radialis: Flexes wrist and abducts hand
• Extensor Digitorum: Extends fingers

Hip and Leg Muscles

• Gluteus Maximus: Extends the hip
• Gluteus Medius: Abducts and rotates the thigh
• Quadriceps: Extends knee
• Hamstrings: Flex knee and extend hip
• Tibialis Anterior: Dorsiflexes and inverts the foot
• Gastrocnemius: Plantar flexes foot (calf muscle)
• Soleus: Aids in plantar flexion

Types of Muscle Tissue

• Skeletal: Attached to bones, voluntary, striated, multinucleated which allows movement, posture, and heat production, with fast contraction
• Cardiac: Heart Walls, involuntary, striated, uninucleated with intercalated disks which pumps blood, rhythmic moderate contraction
• Smooth: Walls of hollow organs (stomach, intestines, blood vessels), involuntary, non-striated, allows movements of substances through organs with sustained slow contractions

Physiology of Muscle Movement

• The sliding filament theory explains how muscles contract

Nerve Signal Initiation

• A motor neuron releases acetylcholine at the neuromuscular junction
• Acetylcholine (ACh) binds to receptors on the muscle cell membrane (sarcolemma), resulting in depolarization

Action Potential and Calcium Release

• The electrical impulse (action potential) spreads through the muscle
• The sarcoplasmic reticulum (SR) releases calcium ions

Cross-Bridge Formation

• Calcium binds to troponin, shifting tropomyosin and exposing myosin-binding sites on actin
• Myosin heads attach to actin, forming cross-bridges

Power Stroke

• Using ATP, myosin pulls actin filaments toward the center of the sarcomere, shortening the muscle
• The H-Zone disappears as filaments slide over each other

Relaxation

• Acetylcholinesterase (AChE) breaks down ACh, stopping the signal
• Calcium is pumped back into the SR
• Myosin detaches, and the muscle relaxes

Energy Sources for Muscle Contraction

• ATP is the primary energy source but limited.
• The creatine phosphate system transfers phosphate to regenerate ATP, and lasts 15 seconds.
• Aerobic respiration needs oxygen to produce 32 ATP and is slower but efficient
• Anaerobic glycolysis produces 2 ATP and lactic acid, leading to fatigue

Types of Muscle Contractions

Isotonic Contraction

• Muscle shortens with movement
• Examples include lifting weights and running

Isometric Contraction

• Muscle generates tension but does not shorten
• Examples include when pushing against a wall and planking

Muscle Fatigue and Oxygen Debt

Causes of Fatigue

• Reduced ATP
• Ion imbalances
• Lactic acid accumulation

Oxygen Debt

• Recovered after exercise with deep breathing

Types of Body Movements

• Flexion: Decreases joint angle
• Extension: Increases joint angle
• Rotation: Movement around an axis
• Abduction: Moving a limb away from the midline
• Adduction: Moving a limb toward the midline
• Circumduction: Circular motion
• Dorsiflexion: Lifting foot upwards
• Plantar Flexion: Pointing toes downward
• Inversion: Turning the sole of the foot inward
• Eversion: Turning the sole of the foot outward
• Supination: Palm facing up
• Pronation: Palm facing down
• Opposition: Thumb touching fingers

Muscle Groups and Their Roles

• Prime Mover (Agonist): Main muscle responsible for movement
• Antagonist: Opposes the prime mover
• Synergist: Assists the prime mover
• Fixator: Stabilizes the origin of the prime mover

Muscular System Conclusion

• Skeletal muscles enable voluntary movement, cardiac muscle pumps blood, smooth muscles move substances, the sliding filament theory explains muscle contraction, and muscle movements vary based on contraction type and energy use

Nervous System

• Is responsible for processing sensory information, controlling body movements, and maintaining homeostasis

Central Nervous System (CNS)

• Brain: The control center.
• Spinal Cord: The communication highway.

Peripheral Nervous System (PNS)

• Cranial and Spinal Nerves: Connect the CNS to the rest of the body

Nervous System Divisions

• Sensory (Afferent) Division: Carries impulses from sensory receptors to the CNS
• Motor (Efferent) Division: Carries signals from the CNS to muscles and glands

Somatic Nervous System

• Voluntary and controls skeletal muscles

Autonomic Nervous System

• Involuntary and regulates cardiac muscles, smooth muscles, and glands
• Two divisions: sympathetic (fight or flight) and parasympathetic (rest and digest)

Regional Functions of the Brain and Spinal Cord

Cerebrum

• Control voluntary movements, emotions, learning, and problem-solving
• Frontal lobe for reasoning, planning, speech & movement
• Parietal lobe for touch, temperature, and pain
• Temporal lobe for hearing, meory, and language
• Occipital lobe for vision processing

Diencephalon

• Thalamus relays sensory information to the cerebral cortex
• Hypothalamus regulates hormones, temperature, hunger, and the autonomic nervous system

Brainstem

• Controls vital functions
• Midbrain controls reflexes for vision and hearing
• Pons assists in breathing regulation
• Medulla oblongata controls heart rate, breathing, and blood pressure

Cerebellum

• Coordinates movement, balance, and posture

Spinal Cord

• Extends from the brainstem down to the lumbar vertebrae
• Conducts impulses between the brain and body
• It contains gray matter (processing and reflexes) and white matter (transmission of signals)
• The dorsal root enables sensory input, and the ventral root controls motor output
• Functions in spinal reflexes which allow rapid, automatic responses to stimuli

Interconnection of Neuronal Networks Defining Specific Functions

• Neurons communicate through networks that allow sensory input, integration, and motor output

Neuron Types

• Sensory (Afferent) Neurons: Carry information from sensory receptors to the CNS
• Motor (Efferent) Neurons: Transmit commands from the CNS to muscles or glands
• Interneurons: Found within the CNS, connecting sensory and motor neurons

Signal Transmission in Neurons

• Inside of the neuron is in a negative resting state but outside of the neuron is positive, when a signal is sent these charges are switched and an action potential is received
• Action Potential: When stimulated, sodium (Na+) rushes in, reversing polarity
• Signal propagates along the axon
• The neuron resets by using the sodium-potassium pump (3 Na+ out, 2 K+ in)

Synaptic Transmission

• When an electrical signal reaches the axon terminal, neurotransmitters are released into the synaptic cleft
• The neurotransmitters trigger the next neuron, continuing the transmission

Reflex Arc

• Example of Neuronal Network: A reflex arc is a direct connection bewteen sensory and motor neurons to bypass the brain
• A receptor detects a stimulus
• Sensory neurons transmit the signal to the spinal cord which is then processed by an interneuron
• An interneuron processes the signal
• A motor neuron sends a command
• An effector reacts

Nervous System Conclusion

• The nervous system is divided into the CNS and PNS, with specialized regions for different functions, and the brain controls higher-order processes, and the spinal cord relays those orders
• Neurons communicate via electrical and chemical signals, forming networks that regulate body functions; reflex arcs allow for fast, automatic responses

Special Senses

• Include smell, taste, sight, hearing, and equilibrium by using specialized sensory receptors

The Eye (Vision)

• The eye provides vision through light detection by rods and cones

Eye Accessory Structures

• Eyelids & Eyelashes/Lacrimal Apparatus: The first protects the eye from debris, and the second produces tear
• Extrinsic Eye Muscles: Six muscles that control eye movement

Eye Internal Structures

• Fibrous Layer (Outer): Sclera (maintains shape) , and Cornea (refracts light into the eye)
• Vascular Layer (Middle): Choroid (Supplies blood to the eye), Iris (Controls pupil size and regulates light entry), Ciliary Body (Adjusts lens shape for focusing
• Sensory Layer (Inner): Retina (Contains photoreceptors (rods and cones))
• Rods detect black, white, and gray
• Cones detect color
• Optic Disc has no photoreceptors
• Fovea Centralis has cones for sharp vision

Lens and Humors

• The lens focuses light onto the retina
• Aqueous Humor provides Nutrients to the cornea and lens
• Vitreous Humor helps to Maintain eye shape

Common Vision Problems:

• Myopia are blurry distant objects because the eyeball is too long
• Hyperopia are blurry near objects because the eyeball is too short
• Astigmatism is blurred vision due to Irregular lens/cornea curvature

Eye Reflexes

• Photopupillary reflex occurs when pupils constrict in bright light
• Accommodation Pupillary Reflex occurs when pupils adjust when focusing on near objects

Hearing & Equilibrium (The Ear)

• The ear enables hearing by using the cochlea and Maintains balance through the vestibular system

Outer Ear Structures

• Pinna (Auricle): Funnels sound into the ear canal
• External Auditory Canal: Contains earwax to trap debris
• Tympanic Membrane (Eardrum): Vibrates with sound waves

Middle Ear

• Ossicles (Tiny Bones): Malleus → Incus → Stapes
• Eustachian Tube: Equalizes pressure between the middle ear and throat

Inner Ear

Cochlea: Converts sound vibrations into nerve impulses

• Vestibule: Detects a static equilibrium
• Semicircular Canals: Detects a dynamic equilibrium

Hearing Process

• Sound waves enter the external ear and vibrate the eardrum
• The ossicles amplify vibrations to the oval window
• Vibrations create pressure waves in the cochlear fluids
• The spiral organ of Corti (hair cells) detects sound and sends impulses via the cochlear nerve to the brain

Balance and Equilibrium

• Static Equilibrium is detected the moment otoliths are shifted by gravity, and these otoliths move fluid
• Dynamic Equilibrium is detected rotational movement by endolymph fluid flow

Hearing & Equilibrium Disorders

• Conduction Deafness occurs when sound waves cannot reach the cochlea
• Sensorineural Deafness is Damage inflicted to hair cells, and auditory nerve
• Ménière's Syndrome is disorder within the inner ear

Chemical Senses

• Taste and Smell use chemical to send signals to the brain and work together

Smell

• Olfactory Receptors: Located in the roof of the nasal cavity
• Olfactory Nerve sends signals to the olfactory cortex in the brain
• Chemicals for this process must be dissolved in mucus for detection

Taste

• Uses the taste buds found on the tongue, soft palate, pharynx, and cheeks
• Taste Papillae
• Fungiform (front)
• Vallate (back)
• Foliate (sides)
• Gustatory Cells: Detect taste molecules dissolved in saliva
• Facial Nerve (Anterior 2/3)
• Glossopharyngeal Nerve (Posterior 1/3)
• Vagus Nerve Throat & epiglottis
• Sweet, amino acids, acids, alkaloids, metal ions, glutamite
• There are five basic tastes

Developmental Aspects of Special Senses

• Vision: Newborns are farsighted and develop color vision & depth perception over time
• Hearing: Reflexives, responding to sounds from birth
• Taste & Smell: Most acute at birth; decline with age

Age-Related Changes

• Presbyopia: Lens loses elasticity
• Cataracts: Lens becomes cloudy
• Presbycusis: Age-related hearing loss
• Olfactory & Gustatory Decline: Fewer receptors, reduced sensitivity

Special Senses Conclusion

• The special senses are sight, hearing, and equilibrium and all of them decline with age