physiology midterm 1 (7) Flashcards
what are the levels of organization in a cell?
cell, tissue, organ, organ system, organism (5 in total)
what are the functions of the cell?
1 nutrients, oxygen 2 exchange materials 3 intracellular transport 4 metabolism or producing atp through sugar and fats 5 synthesis (synthesizing proteins) 5 reproduction ( mitosis)
how big is a cell?
They vary in size, diversity in cells
About 30 microns
What are the largest/ smallest cells?
Neurons are the largest cell in terms in length
Eggs are the biggest cell in terms of diameter
Muscle cells are “quite large”
How many cells in the human body?
37 trillions of cells
The Cell - Levels of Organization:
I Plasma membrane
II - Nucleus
III - Cytoplasm
Organelles
1 - ER (Endoplasmic Reticulum)
2 - Golgi complex
3 - Lysosomes
4 - Peroxisomes
5 - Mitochondria
Cytosol
the water part of the cell
Cytoskeleton
1 - Microtubules
2 - Microfilaments
3 - Intermediate filaments
Nucleus
control center of the cell, containing most of the cell’s genetic material (DNA)
Mitochondria
Known as the “powerhouse” of the cell, mitochondria are responsible for producing energy through cellular respiration. They convert glucose and oxygen into ATP (adenosine triphosphate), which powers various cellular processes.
Ribosomes:
Ribosomes are the sites of protein synthesis. They can be found floating freely in the cytoplasm or attached to the rough endoplasmic reticulum. Ribosomes read mRNA (messenger RNA) sequences and translate them into proteins by assembling amino acids in the correct order.
Golgi Complex
The Golgi complex is involved in modifying, sorting, and packaging proteins and lipids for secretion or delivery to other parts of the cell. It receives proteins from the endoplasmic reticulum and processes them before sending them to their destination, such as the cell membrane or lysosomes.
Rough Endoplasmic Reticulum (ER):
This form of ER has ribosomes attached to its surface, giving it a “rough” appearance. It is primarily involved in the synthesis and modification of proteins, which are often transported to the Golgi complex for further processing.
Smooth ER:
Lacking ribosomes, the smooth ER is involved in lipid synthesis, detoxification of drugs and poisons, and calcium ion storage. It also plays a role in carbohydrate metabolism.
Peroxisomes:
Peroxisomes are small, membrane-bound organelles that contain enzymes responsible for breaking down fatty acids and detoxifying harmful substances, including hydrogen peroxide (H₂O₂). They also play a role in lipid metabolism and the synthesis of bile acids.
Lysosomes:
Lysosomes are membrane-bound organelles containing digestive enzymes that break down waste materials, cellular debris, and foreign invaders such as bacteria. They play a key role in the cell’s waste disposal and recycling processes.
Microfilaments
These are thin, thread-like protein fibers made of actin. They are involved in maintaining cell shape, enabling cell movement, and supporting cell division and muscle contraction.
Microtubules
These are larger, hollow tubes made of tubulin proteins. Microtubules maintain the cell’s structure, serve as tracks for intracellular transport, and play a critical role in cell division by forming the mitotic spindle that separates chromosomes.
Plasma membrane
Thin membrane enclosing each cell
Composed of phospholipid bilayer
hydrophilic , polar heads
Hydrophobic nonpolar tails
Membrane proteins
Channels and carriers to transport molecules and ions
Receptors to signal response (activates some process in the cell)
Form adhesions and junctions
DNA
Genes are blueprint for protein synthesis
Dna is replicated during cell division
RNA
carries out protein synthesis
Messenger RNA
Dna’s genetic copd is transcribed to mRNA and message leaves the nucleus
Ribosomal RNA
Participates in reading the message and translates it into the appropriate protein sequence
Transfer RNA
Transfers the appropriate amino acids form the cytoplasm to their designated site in the protein constructed
Cytoplasm
Portion of cells interior occupied by the nucleus
Organelles
Membrane enclosed structures that carry put specific functions 5 main types are similar in all cells
endoplasmic reticulum
Continuous fluid filled network of membranous tubules
ROUGH ER: ER membrane covered with ribosomes (sites of protein synthesis)
SMOOTH ER: ER membrane lacking ribosomes
Golgi complex
Process raw materials into finished products and directs products to their destination
Exocytosis
atp process in which a cell directs the contents of secretory vesicles out of the cell membrane and into the extracellular space
At which 2 locations in the cell can you find ribosomes ?
rough endoplasmic reticulum
Free floating in the plasma membrane
The golgi can sort proteins to one of which 3 locations?
Outside the cell
Plasma membrane
Lysosomes
Why can a protein made in the ER not end up in the cytoplasm ?
Proteins made in the ER are tagged and transported in vesicles, ensuring they do not mix with cytoplasmic proteins.
Lysosomes
Membrane-enclosed sacs containing hydrolytic enzymes
Material to be digested by lysosomes enters the cell via endocytosis
Pinocytosis
The process by which fluid and dissolved chemicals and molecules are taken in by the cell
Receptor
mediated endocytosis: a process where cells take in molecules from their environment using vesicles made from the plasma membrane.
Phagocytosis
cell eating - invagination of the plasma membrane to form a lathe vesicle and internalize large particles such as bacteria or tissue debris
Peroxisomes
membrane enclosed sacs containing oxidative enzymes which act to remove hydrogen from toxic molecules
Catalase
antioxidant enzyme converting H2O2 into H2O and O2
Mitochondria:
responsible for aerobic metabolism and production of cellular energy
Biochemical way to store and use energy
Glycolysis
occurs in cytosol
Does not require oxygen
Yields 2 ATP
Electron transport
Occurs in mitochondria
Requires oxygen
Yields 28-32 ATP
Cytosol
semi liquid portion of the cytoplasm
Enzymatic regulation of intermediate metabolism
Ribosomal protein synthesis
Storage of fat and glycogen
cytoskeleton
protein network for structural support, transport and cellular movement (3 major components)
Microtubules
Microfilaments
Intermediate filaments
Microtubules:
maintain cell shape and control axonal transport, movement of cilia, flagella and chromosomes
Long, hollow tubes formed by slightly different variants of small, globular tubulin molecules
Axonal transport:
bidirectional movement of large molecules and vesicles along the axon of neurons
Cilia
motile, hair like protrusions on cell surface (respiratory pathway, oviduct, brain ventricles)
Flagella
enables sperm movement
Examples of cell types
Neuron
Pancreatic cells
Immune cells
Egg and sperm
Muscle
Skeletal
Cardiac
Smooth
Nervous (signals)
Central
Peripheral
Connective (structure support)
Tendons
Bones
Blood
Epithelial (exchange) 4
- Epithelial sheets (form boundaries)
- Glands (secretion)
- Exocrine (external secretion)
- Endocrine (internal secretion)
Epithelial sheet
barrier to digestive juices
Exocrine gland
secretes digestive juices
Endocrine gland
regulates exocrine secretion
Peripheral nerves
regulate contraction
CLAUDE BERNARD
Organism can effectively have an internal environment that can be controlled independently from outside fluctuations
WALTER B CANNON
Coined the concept of homeostasis
hemostatis
Dynamic maintenance of a stable internal (extracellular) environment within the organism
Essential to survival of each cell
Requires continual exchange of material between the intrace;lular and extracellular spaces
Each organ system contributes by contracting changes of internal environment
Negative feedback
change in controlled variable triggers a response that opposes the change
Sensor
mechanism to detect the controlled variable
Integrator
compares the sensors input with the set point
Effector
adjusts the value of the controlled variable
Positive feedback
reinforces the change in a controlled variable, occurs relatively rarely
Feedforward control
response occurring in anticipation of a change in a control variable
Nervous system (neurotransmitters
rapid, short acting signals, network through synapses
Gap junctions
proteinaceous tunnels that permit free diffusion of small molecules from one cell to the other
Transient direct contact via cell surface receptors, they can be linked to intracellular cascades
Endocrine system (hormones)
slower acting, longer lasting signals. Network based on diffuse via bloodstream
Our brains
Receive sensory input (eg visual auditory, somatosensory, olfactory and gustatory) and produce motor output.
Shown above are the early stages of the human visual system from retina (in the eye) to primary visual cortex.
Cortext
the site of conscious perception = what you can report on
The human brain consists of ____ which are cells specialized for electrical and chemical signaling.
86 billion neurons
Electrical signals
(including action potentials) are propagated with neurons
Neurons
communicate with other neurons using chemical messengers called neurotransmitters
Neurotransmitters are released and detected at
synapses
The human brain contains
> 100 trillion synaptic connections
How can ions and glucose get across the membrane ?
Transporter proteins, Ion channels (channel proteins)
Transporter proteins
Are used to escort molecules across the membrane that cant diffuse unassisted
This is also called carrier-mediated transport
One example is the glucose transporter which allows cells to take up glucose from the blood
Ion channels (channel proteins)
Are different types of membrane proteins needed for electrical signaling in neurons, muscle and cardiac tissue
They are permeable to specific ions such as Na+ or K+
Transporters
Carrier mediated transport is a mechanism for moving substances across the plasma membrane when the substance cannot simply diffuse through the membrane
Transporters have binding sites specific for their
ligand
Transporters can be saturated
This means that there is a maximum flux of molecules/ unit of time that is possible
Protein Targeting from the ER
Proteins made in the ER are directed to specific locations via vesicles and cannot enter the cytoplasm. This ensures proper protein sorting within the cell.
Affinity Change:
The binding site changes affinity for the molecule, enabling two separate conformational shifts (one for affinity, one for gating between ICF and ECF).
Active Transport
Pumps move molecules uphill (against the concentration gradient) using ATP, classifying them as active transport.
Na/K ATPase:
this pump moves 3 Na⁺ out and 2 K⁺ into the cell per cycle, powered by ATP.
1. Maintain Na⁺ and K⁺ concentration gradients.
2. Regulate osmotic balance.
3. Create energy gradients for co-transport.
Energy Use for Na⁺/K⁺ ATPase
The Na⁺/K⁺ pump consumes about 55% of a neuron’s ATP supply, indicating its importance.
Continuous Operation for Na⁺/K⁺ ATPase
it runs constantly and is largely unregulated (constitutive process).
Role in Signaling:
its key function is to establish and maintain Na⁺ and K⁺ concentration gradients, crucial for electrical signaling.
ION CHANNELS
Membrane proteins permeable to certain ions
There are 100 different types of ion channels, each coded for by a different gene
Channels differ in selectivity, gating and permeability
Selectivity
which ions can permeate
Permeability
the capacity for ion flow
gating
ligand-gated, voltage-gated, mechanically-gated.. Or always open
Once open ions move in response to two driving forces:
Chemical driving force
Electrical driving force
Down a concentration gradient
= net movement of solute molecules form an area of high concentration to an area of lower concentration
Diffusion is due to
thermal motion which results in random collisions
THE ELECTRICAL DRIVING FORCE
Movement of charged particles along an electrical gradient is due to electrostatic attraction (opposite charges) or repulsion (like charges)
This is action at a distance
RESTING MEMBRANE POTENTIAL
Voltage differences across the plasma membrane, in millivolts, when the cell is at rest (i.e no perturbing influences)
Often abbreviated as Vm
HOW DOES THE CELL CREATE CHARGE SEPARATION?
1
Establishes and maintains concentration gradient for key ions: Na+, K+ and A-
HOW DOES THE CELL CREATE CHARGE SEPARATION? 2
Na+ and K+ ions diffuse through the membrane down their concentration gradients. This occurs through Leak Channels
HOW DOES THE CELL CREATE CHARGE SEPARATION? 3
Diffusion through the membrane results in charge separation, creating a membrane potential
HOW DOES THE CELL CREATE CHARGE SEPARATION? 4
Net movement of charges continues until the forces exerted by the electrical gradient exactly counterbalances the force exerted by the concentration gradient. This is the resulting potential.
Concentration Gradients
The Na⁺/K⁺ ATPase pumps 3 Na⁺ out and 2 K⁺ in, creating a net movement of 1 positive charge per cycle.
This charge separation contributes only ~15% to the resting potential.
Its primary role is to maintain low intracellular Na⁺ and high intracellular K⁺ concentrations.
Na+/K+ ATPase pumps
Na⁺: Low inside due to Na⁺/K⁺ pump.
K⁺: High inside due to Na⁺/K⁺ pump.
Anions (A⁻): High intracellular levels of negatively charged macromolecules like proteins and nucleic acids.
Resting Membrane Potential (RMP)
RMP is the membrane potential when the neuron is not influenced by external factors like action potentials or synaptic activity. It reflects the equilibrium of Na⁺ and K⁺ ions.
At Rest Na⁺ Leak
Na⁺ leaks both in and out through leak channels
At Rest K⁺ Leak:
K⁺ also leaks both in and out, but more K⁺ leaks out due to higher permeability of K⁺ at rest.
At Rest, Net Effect
There’s more Na⁺ leakage into the cell, but K⁺ leakage dominates due to stronger K⁺ permeability.
Membrane permeabilities change during
cell activity.
Ion movements that generate RMP are small compared to overall
ion concentrations.
At rest, there is a slight inward trickle of ___ and an outward trickle of ___ , but no net charge movement.
Na+ , K+
Net Electrochemical Driving Force (DFnet)
: DFnet is the total force acting on each ion at any given moment.
(DFnet) Membrane Potential (MP)
As the MP changes, the electrical driving force changes, altering DFnet.
(DFnet) Role:
DFnet determines the direction and size of ion flow, influencing currents during action potentials and synaptic activity.
Graded Potentials
like a small, localized electrical ripple on a neuron’s membrane that gets bigger or smaller depending on how strong the stimulus is
Discovery of the Ionic Basis of the Action Potential: The Squid Giant Axon
Invertebrate axons can be up to one million times larger in volume than human axons, making them easier to study.
In the 1930s, Alan Hodgkin and Andrew Huxley shifted from radar analysis during WWII to studying the brain.
They discovered the ionic basis of the action potential and won the Nobel Prize in 1963.
Action Potential
An action potential is a brief, all-or-nothing reversal of membrane potential, lasting about 1 millisecond.
It occurs due to rapid changes in membrane permeability to Na+ and K+ ions.
“Bulk” permeability refers to the presence of many individual channels within a membrane patch.
THRESHOLD
Once the threshold potential is crossed, depolarization occurs via a positive feedback loop
Voltage gated Na+ channels
opens quickly (<0.5 ms) in response to depolarization, allowing Na+ to flow down its electrochemical gradient into the cell. Responsible for rising phase of AP
Voltage gated K+ channel:
opens more slowly in response to depolarization allowing K+ ions to flow out f the cell down their electrochemical gradient
Responsible for falling phase of AP and for the after hyperpolarization, or AHP
VOLTAGE GATED Na+ CHANNEL HAS THREE STAGES
Deactivated = closed but capable of opening
activated= open
inactivated= closed and not capable of opening, can only be removed by repolarization to 70mv
VOLTAGE GATED K+ CHANNEL HAS TWO STATES
deactivated= closed but capable of opening
Deactivated= closed but capable of opening
activated= open
Absolute refractory period
is a brief period during which a second spike cannot be generated
It begins with the activation of voltage-gated Na+ channels and ends when their inactivation is removed
Relative refractory period
is a brief period following a spike during which higher intensity stimulus is needed to generate a second spike
It begins when Na+ channel inactivation is removed and ends the voltage-gated K+ channels deactivate
Peacemaker cells
are intrinsically autorhythmic. Their membrane potential slowly depolarized between APs, drifting to threshold
Peacemaker cells initiate APs that spread through the heart to trigger contractions
Cardiac cells:
are contractile and do not initiate their own APs
Axon Size and Resistance
Human axons must be much smaller in diameter to fit in the brain, leading to high axial resistance.
Without adaptation, current would leak across the membrane (transverse pathway).
Evolution increased transverse resistance with myelin to prevent leakage.
Myelin
A multi-layered sheath of plasma membrane from specialized glial cells that insulates axons.
Despite high axial resistance in small mammalian axons,
myelin ensures current flows along the axon, not through the membrane.
Nodes of Ranvier
gaps in myelin with a high density of voltage-gated Na+ and K+ channels
SYNAPSE
Synapse are junctions between two neurons, or between a neuron and a muscle or gland that enables one cell to electrically and/or biochemical influence another cell
ELECTRICAL SYNAPSE
Discovered in the crayfish nervous system by Ed Furshpan and David Potter in 1959
Direct connections between neurons via gap junctions, allowing rapid, bidirectional flow of electrical signals without neurotransmitters.
CHEMICAL SYNAPSE
- Action potential propagation in presynaptic neuron
Ca2+ entry into synaptic knob - Release of neurotransmitter by exocytosis
- Binding of neurotransmitter by exocytosis
- Binding of neurotransmitter to postsynaptic receptor
- Opening of specific ion channels in subsynaptic membrane
Excitatory postsynaptic potential (EPSP)
Deporlaizinh events that bring Vm closer to threshold for firing an actions potential
Common excitatory neurotransmitters include glutamate (Glu) and acetylcholine
inhibitory postsynaptic potential (IPSP)
Hyperpolarizing events that bring Vm away from threshold for firing an action potential
Common inhibitory neurotransmitters include GABA and glycine (Gly)
Fast Synapses and Ligand-Gated Ion Channels:
The exoplasmic domain of a ligand-gated receptor contains a neurotransmitter-binding site.
Binding of the neurotransmitter causes an immediate conformational change, opening the channel and allowing ions to cross the membrane.
This results in changes in the membrane potential within 0.1 to 2 milliseconds.
Transmitter Removal, Degradation
Extracellular enzymes break down neurotransmitters.
Slow Synapses and Receptors Coupled to G Proteins:
Nervous system functions like heart rate regulation operate over seconds or minutes.
Neurotransmitter actions over slow synapses often last several seconds and involve G protein-coupled receptors (GPCRs).
Transmitter Removal, Diffusion:
Neurotransmitters diffuse out of the synaptic cleft, resulting in dilution.
Transmitter Removal, Reuptake
Transporter proteins take neurotransmitters back into the presynaptic terminal.
Neuronal Integration
Convergence: is the synaptic input of many neurons on to one neuron
Divergence: the synaptic output of one neuron knot many neurons
Brain Function Overview
Processes sensory inputs and generates motor outputs.
Conscious perception and sensory-motor transformation happen in the brain.
Sensory inputs flow into the brain, producing motor outputs.
CNS:
Brain and spinal cord.
PNS:
Neural tissue outside the CNS
Afferent division:
Sends sensory info to the CNS.
Efferent division
Sends motor signals from CNS to effectors
Somatic nervous system
Controls voluntary movement.
Autonomic nervous system:
: Controls involuntary functions (sympathetic and parasympathetic).
Spinal Column Structure, Gray matter
Contains cell bodies.
Spinal Column Structure, White matter
Contains myelinated axons.
Spinal Column Structure, Dorsal root
Carries sensory input (afferent).
Spinal Column Structure, Ventral root
Sends motor output (efferent).
Spinal Column Structure, Interneurons:
Local processing within the spinal cord.
Frontal lobe:
Motor control, planning, personality.
Parietal lobe
Sensory integration.
Temporal lobe:
Auditory processing, memory.
Occipital lobe
Visual processing.
Sensory Homunculus
Represents body parts in the somatosensory cortex.
Larger areas for body parts with higher sensory importance (e.g., hands, face).
Motor Homunculus
Represents body parts in the primary motor cortex.
Larger areas for body parts requiring fine motor control (e.g., hands, face).
Autonomic Nervous System (ANS), Sympathetic division (SD)
Prepares body for “fight or flight.”
Autonomic Nervous System (ANS), Parasympathetic division (PD)
Maintains “rest and digest” functions.
Both SD and PD control various organs like the
heart, lungs, and digestive system.
ANS Anatomy and Neurotransmission, SD:
Short preganglionic, long postganglionic neurons; uses norepinephrine (NE).
ANS Anatomy and Neurotransmission, PD:
Long preganglionic, short postganglionic neurons; uses acetylcholine (ACh).
ANS Anatomy and Neurotransmission, Adrenal medulla
Directly innervated by SD, releases epinephrine into the bloodstream.
Nicotinic ACh receptors:
On all postganglionic neurons, cause depolarization.
Muscarinic ACh receptors:
On parasympathetic target tissues.
Adrenergic receptors:
Respond to NE and epinephrine in the sympathetic system.
Sympathetic
“Fight or flight”
Relay Nuclei
Process receptor signals and send to thalamus.
Parasympathetic:
“Rest and digest”
Sensory Function
Detect external events.
Sensory Systems
6 total in mammals; 5 pass through the thalamus, olfactory is direct to cortex.
Receptors
Transduce stimuli into neuronal signals.
Thalamus
Relays to primary cortex.
Cerebral Cortex, Primary
Initial processing.
Cerebral Cortex, Secondary:
Further processing, sends to association areas.
Receptor Potential:
Change in membrane potential at transduction site.
Voltage-gated:
e.g., Pacinian corpuscles.
Chemical messenger-gated:
e.g., photoreceptors.
Receptive Field
Region where stimuli influence neuron activity
Modality Specificity
Receptors respond to specific stimuli.
Examples: Photoreceptors (light), Pacinian corpuscles (pressure).
Visual System: Receptors:
Photoreceptors (rods and cones).
Visual System:Cortex:
Primary visual cortex (V1).
Visual System: Thalamic relay:
Lateral geniculate nucleus.
Auditory System: Cortex
Auditory cortex.
Auditory System: Thalamic relay
Medial geniculate nucleus.
Auditory System: Receptors:
Hair cells in cochlea.
Somatosensory System: Cortex:
Primary somatosensory cortex (S1).
Somatosensory System: Thalamic relay
Ventral posterior nucleus.
Somatosensory System: Somatosensory System:
Mechanoreceptors (Pacinian corpuscles, Merkel cells).
Gustatory System (Taste): Cortex:
Gustatory cortex.
Gustatory System (Taste): Thalamic relay
Ventral posterior medial nucleus
Gustatory System (Taste) Receptors:
Taste buds.
Olfactory System (Smell): Cortex:
Olfactory cortex.
Olfactory System (Smell): Receptors
Olfactory receptor neurons (no thalamic relay).
Vestibular System (Balance): Cortex:
Vestibular cortex.
Vestibular System (Balance): Thalamic relay:
Ventral posterior nucleus.
Vestibular System (Balance): Receptors:
Hair cells in semicircular canals and otolith organs.
Eye Anatomy
Cornea, lens, iris, retina, optic nerve.
Retina Layers:
Photoreceptors (rods and cones), bipolar cells, ganglion cells.
Visual Processing
Light enters, processed from photoreceptors to ganglion cells.
Fovea:
Area of highest visual acuity.
Acuity:
Ability to discriminate between stimuli
Two-point discrimination
Measures minimum distance perceived as separate points.
Phototransduction, Light:
Rhodopsin active, cGMP low, Na+ channels close, cell hyperpolarizes (-70 mV).
Phototransduction, Darkness
Rhodopsin inactive, cGMP high, Na+ channels open (-40 mV).
Photoreceptors, Rods:
Sensitive to low light (scotopic vision), low acuity, peripheral vision.
Minimum audible angle (MAA):
Smallest detectable change in sound position.
Photoreceptors, Structure:
Outer segment (light absorption), inner segment (cell machinery), synaptic terminal.
Photoreceptors, Cones
Sensitive to bright light (photopic vision), color vision, high acuity.
Phototransduction, Recovery:
Rhodopsin reforms, neurotransmitter release adjusts to light.
Color Perception, Cone Types
Blue (~420 nm), green (~530 nm), red (~560 nm).
Perception:
Based on relative stimulation of cones.
Visual Pathways
Optic nerve, chiasm, tract, radiation to occipital lobe.
Visual Deficits
Left optic nerve damage: Left eye blindness.
Optic chiasm damage: Temporal field loss in both eyes.
Left optic tract damage: Right visual field loss in both eyes.
Middle Ear
Ossicles, oval window.
External Ear
Pinna, ear canal, tympanic membrane.
Inner Ear
Cochlea (hearing), vestibular apparatus (balance).
Basilar Membrane
Responds to different frequencies along its length (high near base, low near apex).
Somatosensory Receptors, Types
Mechanoreceptors (touch), nociceptors (pain), thermoreceptors (temperature).
Somatosensory Receptors, Pacinian Corpuscle
Rapidly adapting, detects pressure and vibration.
Primary Auditory Cortex:
Tonotopic organization (frequencies correspond to specific cortical areas).
Organ of Corti:
Contains hair cells; sound waves cause hair cell deflection, opening ion channels.
Tonotopic Organization
High frequencies at the base, low frequencies near apex.
Somatosensory Pathways:
Sensory info travels from skin → spinal cord → medulla → pons → thalamus → somatosensory cortex
Pain pathways are separate
Vertebrate Column Organization:
Cervical, thoracic, lumbar, sacral, coccygeal segments
Motor neurons at each segment control ipsilateral skeletal muscles
Spinal nerves emerge at each vertebral level
Motor Control (Cerebellum)
Compares intended vs actual movement, makes adjustments
Motor cortex initiates commands, cerebellum refines based on feedback
Somatic Motor Pathway:
Controls skeletal muscles via motor neurons in the ventral root
Uses acetylcholine (ACh) as neurotransmitter at neuromuscular junction
Nicotinic ACh receptors on muscle fibers; ACh degraded by acetylcholinesterase
Neuromuscular Junction:
Synapse between motor neuron and muscle fiber
ACh release → binds receptors → muscle depolarization → contraction
Voluntary Movement:
Motor cortex initiates voluntary movement
Corticospinal tract connects cortex to spinal cord
Damage can cause cerebral palsy due to hypoxic stress during childbirth
Withdrawal and Extensor Reflexes:
Pain triggers reflex: flexor contracts, extensor relaxes on the stimulated side
Opposite response on contralateral side to maintain balance
Parkinson’s Disease:
Degeneration of dopaminergic neurons in basal ganglia
Symptoms: difficulty initiating movements, resting tremors
Multiple Sclerosis (MS):
Autoimmune destruction of myelin sheaths
Symptoms: impaired movement control, action tremors
Myasthenia Gravis:
Autoimmune disease affecting ACh receptors at neuromuscular junction
Symptoms: muscle weakness, drooping eyelids (ptosis)
Treatment: acetylcholinesterase inhibitors (e.g., neostigmine)
Wernicke’s area
Language comprehension (left association cortex)
Broca’s area:
Speech production (left frontal lobe)
Functional Localization:
Loss of function: Study behavioral deficits and brain damage
fMRI: Records brain activity during specific behaviors
Examples: Phineas Gage
Angular gyrus:
Integrates language-related areas
Connections
Bundle linking these areas
Damage Effects:
Broca’s area:
Speech production issues
damage effects, Wernicke’s area
Language comprehension deficits
fMRI
Tracks brain regions during specific tasks (e.g., face recognition)
EEG
High temporal resolution, poor spatial resolution
