Neuro/Endo Systems Flashcards
Communication System that detects, processes, and responses to stimuli
Nervous System
Evolutionary concentration of interneurons at anterior end of organism
Cephalization
Type of excitable cell that detects and processes stimuli
Neuron
Structural and metabolic support for neurons
Neuroglia
What are the three types of neurons and their functions
- Sensory: detect stimuli (receptors)
- Interneurons: integrate signals (integrators)
- Motor: signal effectors to perform actions
Two Types of Nervous Systems and function
- Central: Processes and responses to signals
2. Detects and relays signals, responses
Main Nerves in Body and number
Cranial (12 pairs) Cervical (8 pairs) Thoracic (12 pairs) Lumbar (5 pairs) Sacral (5 pairs) Coccygeal (1 pair)
Ulnar (1/arm)
Sciatic (1/leg)
Axons relaying signals into CNS
Afferent
Axons relaying commands from CNS
Efferent
Neuron extensions that receive signals
Dendrites
Neuron extension that sends signal
Axon
Zones of a neuron
Input zone (cell body and dendrites) Trigger zone (special membrane section) Conducting zone (axon) Output zone (axon ending/synapse)
Term for Electric Gradient across neuron not receiving a signal
Resting Membrane Potential ~= -70 mV
Stimulation of excitable cell
Action Potential
An Action Potential is…
an abrupt reversal of the electric gradient across a neuron
Neurons maintain resting potential by…
- actively pumping Sodium out of cell and Potassium into cell
- more potassium, less sodium in cell
-sodium not able to leak back into cell
Action Potential triggers voltage reversal by…
Openings voltage-activated sodium and potassium gates
Steps of an action potential:
- Pressure, other stimulus on sensory neuron deforms membrane, allows ions through. Creates graded potential
- If potential is above threshold level, gated ion channels open, bringing in sodium ions.
- Increasing positive charge of cell leads to more gates opening (positive feedback mechanisms)
- Action Potential self-propagates along conducting zone (axon)
What is the Threshold Level?
Voltage needed to activate gated ion channels in trigger zone
Why is an AP an all-or-nothing event?
Because once the threshold level has been reached, stimulus strength has no bearing on proceeding AP, same number of gates will open due to positive feedback.
Why does an AP flow only one way?
Because after a timeout period, ion gates close and are deactivated for awhile, causing ions to only be able to flow to a new part of the conducting zone.
Point of interaction between two neurons (signal transfer location)
Chemical Synapse
Cell sending a signal across a synapse
Presynaptic cell
Cell receiving a signal across a synapse
Postsynaptic cell
Gap between pre- and postsynaptic cells
Synaptic Cleft
Signalling molecule that relays message between neurosystem cells
Neurotransmitter
Sum of all signals entering an interneurons
Synaptic Integration
Neurotransmitter that induces muscle contractions in smooth muscle, slows cardiac contraction, has roles in mood and memory
Acetylcholine (ACh)
Neurotransmitter that speeds heart rate, dilutes pupils and airway, slows gut contractions, increases anxiety
Epinephrine, norepinephrine
Aka Adrenaline
Neurotransmitter that dampens other neurotransmitters, has roles in memory, learning, fine motor control
Dopamine
Neurotransmitter that elevates mood, has role in memory
Serotonin
Neurotransmitter that inhibits release of other neurotransmitters
GABA
A molecule that influences effects of neurotransmitters
Neuromuscular or
3 ways of removing neurotransmitters from synaptic cleft
- Diffusion back into presynaptic cell/extra cellular fluid
- Pumping back into presynaptic cell or neuroglia
- Breakdown by released enzymes
How does nerve gas work?
Inhibits removal of neurotransmitters from synaptic cleft, negatively impacts ability of cells to signal
Types of Interneuron Circuits
- Diverging: dendrites extend from one block of neurons and axons extend to another
- Converging: many neurons converge their signals on a small number of neurons
- Reverberating: neuron loops signal back on itself
What surrounds axons and what are their purpose?
A myelin sheath made of Schwann cells. It prevents ions from crossing the cell membrane at any point but nodes, which lay between two cells. The nodes are unsheathed but have many Na gates that speed up A.P.s immensely. Allowing rapid signal movement.
Reflex
Autonomic response to a stimulus that does not require any thought
Steps of the stretch reflex
- Force applied to muscle, AP triggered through sensory neurons on deformed muscle spindle
- AP travels to spinal cord
- Neurotransmitter released at spinal cord, stimulates motor neuron
- Motor neuron releases ACh, stimulates muscle fibres
- Muscle contracts
The two classes of nerves in PNS and roles
- Somatic: information to/from skin, tendons, skeletal muscle; responsible for voluntary motion
- Autonomic: information to/from viscera; involuntary actions
2 divisions of autonomic nerves and roles
- Sympathetic: active during stress; fight or flight reflexes
- Parasympathetic: active during relaxation; daily housekeeping, digestion, urine formation
Two types of CNS matter
Grey matter - inner matter: cell bodies, dendrites, unsheathed axons, neuroglia
White matter - outer matter: myelin-sheathed axons, neuroglia
Spinal roots for different neuron types
Dorsal root - sensory/afferent neurons
Ventral root - motor/efferent neurons
Brain can be divided into…
- Cerebrum (higher-order thought, motion)
- Cerebellum (balance)
- Brain Stem (basic life functions)
OR
- Forebrain
- Midbrain
- Hindbrain
Functions of the medulla oblongata
Respiration, circulation, swallowing, coughing, affects sleep
Functions of the Cerebellum
Receives input from muscle spindles, eyes, ears, forebrain regions; controls balance and posture
Functions of the Pons
Controls respiration, connects different parts of brain, controls signal flow
Function of the cerebrum
Processes sensory input, controls muscles, functions in memories, emotion and higher thought
Function of the thalamus
Sorting and relay station, role in memory
Function of the corpus callosum
Connects and coordinates the two brain hemispheres
Clear fluid that cushions brain and spinal cord
Cerebrospinal fluid
Function of the blood-brain barrier
Protects brain from harmful substances, carefully controls homeostasis in the brain by very selectively allowing substances into cerebrospinal fluid.
The lobes of the cerebral cortex
Frontal, parietal, occipital, temporal
Primary Motor Cortex
In frontal lobe, controls and coordinates movements of skeletal muscle
Premotor cortex
In frontal loge, ahead of primary motor cortex
Regulates complex movements and learned motor skills; coordinates actively of multiple muscle groups
Broca’s Area
In frontal lobe
Translates thought to speech, controls tongue, throat, lips for speech
Primary Somatosensory Cortex
Located at front of parietal lobe
Receiving centre for sensory input form skin and joints, part of it deals with taste perception
Primary visual cortex
Back of occipital lobe
Receives input from eyes
Prefrontal Cortex
Front of frontal lobe
Personality, abstract thought, judgement, planning, empathy
The limbic system…
Governs emotions, assists in memory, correlates organ activity with self-gratifying behaviour
Encircles upper brain stem
The functions of the hypothalamus (limbic)
Controls homeostasis
Correlates emotions and visceral activity
Functions of the hippocampus
Helps store and access memories
Functions of the amygdala
Interprets social clues, role in sense of self
Functions of the Cingulate Gyrus
Helps regulate emotions and pain
Involved in predicting and avoiding negative consequences
neuroglia functions
Structure, paths Insulation (Schwann cells) Immune defence Maintaining proper ion concentrations Synthesize various substances (growth factor, lactate) Consume dead cells
Types of signalling molecules
- Hormones - long-distance body communication
- Neurotransmitters - secreted by neurons into synaptic cleft
- Local signalling molecules - secreted by cells, affect only nearby tissue
- Pheromones - air/water dissolved substances that help integrate social behaviour
Main glands of the endocrine system
Hypothalamus Pituitary Pineal Thyroid Parathyroid Thymus Adrenal Pancreas Gonads (ovaries/testes)
Cell sensitivity to hormones is affected by…
Presence of proper receptors Interaction between hormones Concentration of hormone in tissue Cell's nutritional and metabolic state Environment conditions
Hypothalamus (endocrine)
Secretes releasing hormones:
Oxytocin (contractions, lactation, social behaviour)
Antidiuretic hormone (controls amount of H2O lost in urine)
Sends hormones to posterior pituitary gland.
Pituitary Gland
Two lobes: anterior and posterior
Controlled by releasing/inhibiting hormones from hypothalamus
Secretes:
andrenocorticotropic hormone: stimulates release of cortisol
Thyroid-stimulating hormone: stimulates release of thyroid hormone
Growth hormone (somatotropin): promotes bone, tissue growth
Skin-covered cartilage flap of outer ear
Pinna
Bones of the middle ear
Malleus (hammer)
Incus (anvil)
Stapes (stirrup)
Snail-like structure of inner ear
The cochlea
The two ducts of the inner ear
Scala vestibuli
Scalia tympani
Structure of scala media (middle cochlear duct)
Basilar membrane which differentially vibrates
Organ of Corti that has hair cells that stick into the tectorial membrane
Covers the front of the eye
Cornea
Covers the back of eye
Sclera
Provides nutrition for eye and absorbs missed light
Choroid
Muscles that adjust lens shape
Ciliary muscles
Eye structure with photoreceptors
Retina
Lubricates lens and outer eye
Aqueous humour
Fills eyeball and gives structure
Vitreous body
