Week 2 Flashcards
Central Nervous System
Brain and Spinal Cord
Peripheral Nervous System
Cranial nerves, ganglia outside CNS, spinal nerves
Two Types of Sensory Input
External (sensory) and Internal (visceral)
Where input goes, motor output leaves
Central nervous system: Brain and Spinal Cord.
Integration occurs
Two Types of Motor Output
Somatic Nervous System
Autonomic Nervous System
Somatic Nervous System Acts on
Skeletal Muscles
Autonomic Nervous System Acts on
Sympathetic and parasympathetic system (as well as enteric nervous system in digestive tract)
Pathway from CNS to effector organ
CNS –preganglionic fiber–> autonomic ganglion (Preganglionic neurotransmitter) –postganglionic fiber–> Varicosity (Postganglionic neurotransmitter) –> Effector Organ
Sympathetic and Parasympathetic Preganglionic neurotransmitter and Receptor
Acetylcholine, All Nicotinic Receptors
Sympathetic Postganglionic Neurotransmitter
Norepinephrine/Epinephrine
Sympathetic Effector Organ Receptors
Adrenergic Receptors (a1, a2, B1, B2, B3)
Parasympathetic Postganglionic Neurotransmitter
Acetylcholine
Parasympathetic Effector Organ Receptors
Muscarinic Receptors (M1, M2, M3, M4, M5)
General Response of Parasympathetic and Sympathetic
Para: Rest and Digest
Sym : Fight or Flight
Parasympathetic and Sympathetic: Pupils
Para: Constrict
Sym: Dilate
Parasympathetic and Sympathetic: Saliva
Para: Stimulate
Sym: Inhibit
Parasympathetic and Sympathetic: Heartbeat
Para: Slow (Vagus)
Sym: Increase
Heartbeat Responses
Stimulate Vagus: slows
Stimulate Sympathetic nerves: Increase
Cut Sympathetic: Slows
Cut Sympathetic and Parasympathetic: Increase
Which autonomic system has more basal activity on the heart
Parasympathetic – when both nerves cut, heart rate increases rather than remains unchanged
Parasympathetic and Sympathetic: Airways
Para: Constrict
Sym: Relax
Parasympathetic and Sympathetic: Stomach and Intestine Activity
Para: Stimulate
Sym: Inhibit
Parasympathetic and Sympathetic: Glucose Release (Liver)
Sym: Stimulate
Parasympathetic and Sympathetic: Gall bladder
Para: Stimulate
Syn: Inhibit
Parasympathetic and Sympathetic: Bladder
Para: contract (voiding)
Sym: Inhibit
Parasympathetic and Sympathetic: Genitals
Para: Erection
Sym: Ejaculation
Sympathetic Spinal Nerves
T1-T12
Sympathetic Splanchnic Nerves
L1, L2
Parasympathetic Cranial Nerves
IX, Vii, III, X
Parasympathetic Spinal Nerves
S1-S4
Grey Matter
Cell bodies and dendrites
Cerebrum (outside-corex)
White Matter
Axons with myelin
Inside and in tracts
Ventricles
In middle of white matter, hollow spaces in brain
Brainstem
Composed of Midbrain, Pons, and Medulla
Control of cardiovascular, respiration, digestion
Cerebellum
Balance, skilled movement
Hypothalamus
Temperature, Thirst, Hunger, Endocrine
Thalamus
Sensory Relay, Emotion, Arousal
Basal Nuclei
Motor control, addiction, habits
Cerebral cortex
Sensory, motor, association, thinking, etc.
Protection of the CNS
- Bony structures (cranium (skull) encases brain, Vertebral column surrounds spinal cord)
- Cerebrospinal Fluid (CSF) in ventricles formed by selective transport fluids
- Blood-brain barrier - tight junctions between capillary endothelial cells
Cerebral Spinal Fluid
Made by tissue that lines the ventricles (hollow spaces) in the brain. It flows in and around the brain and spinal cord to help cushion them from injury and provide nutrients.
Blood-Brain Barrier
-Tight junction in capillary wall
-Astrocyte processes
-carrier-mediated transport
-lipid soluble substances can get through?
Most capillaries
Possess water-lined pore
Brain highly dependent on
Constant blood supply
- brain cannot produce ATP in absence of oxygen
-Brain uses only glucose (and ketone bodies during starvation) for fuel (small amount of glycogen stored in astrocytes)
- brain damage results if brain is deprived of oxygen for more than a few minutes (stroke)
Four lobes of cerebral corex
occipital, temporal, parietal, frontal
Occipital lobe
Back of brain- contains visual association area (vision)
Temporal lobe
middle of brain- auditory association area
(hearing, smell)
Parietal lobe
Near back of brain on top- contains somatosensory cortex and somatosensory association area (body sensory, touch, taste, speech, reading)
Frontal lobe
Front of brain- contains frontal association area and motor cortex (motor activity, speech, memory, planning)
Hearing hotspot
Middle of brain - auditory cortex in temporal lobe
Seeing words hotspot
Back of brain - visual cortex in occipital lobe
Speaking words hotspot
Middle top of brain- motor cortex in frontal lobe
Generating words hotspot
Front of brain- broca’s area in frontal lobe
Central sulcus
Split down middle of brain between primary motor cortex and somatosensory cortex
Hommunculus
Visual representation of what parts of the brain correspond to each body part (sensory humunculus similar to motor humunculus)
Four distinct structures of the brain
Brainstem, Diencephalon, Cerebellum, Cerebrum
Medulla
In Brainstem. Autonomic center for regulating heart, lungs, and digestive system
Hypothalamus
In Diencephalon. Temperature, hormones, hunger, thirst, sexual behaviors
Thee parts of cerebellum
Vestibulocerebellum, Spinocerebellum, Cerebrocerebellum
Vestibulocerebellum
Bottom and top (closest to brainstem) - Maintenance of balance, control of eye movements
Spinocerebellum
Top (middle) - Regulation of muscle tone, coordination of skilled voluntary movement
Cerebrocerebellum
Bottom- Planing and initiation of voluntary activity, storage of procedural memories
Hypothalamus
- Integrating center for homeostatic functions (body temp, thirst and urine output, food intake)
- Controls anterior pituitary hormone secretion
- Produces posterior pituitary hormones (Stimulates uterine contraction and milk ejection)
Pathway for coordinated movement
frontal lobe plans –> premotor cortex prepares for movement –> primary motor cortex activates movement pathways –> cerebellum receives input from premotor cortex, primary motor cortex and sensory input from parietal lobe SS cortex and cordinates –> coordinated movement comes from premotor and primary motor cortex
Saltatory Conduction
Occurs along myelinated axon. Action potential jumps between nodes of ranvier and increases speed of conduction
Axons synapse on
- Other neurons
- Muscle cells (skeletal, cardiac, smooth)
- Glands
Neuromuscular junction
Occurs between motor neuron and skeletal muscle
1. action potential reaches presynaptic terminal
2. open voltage-gated Ca2+ channels, causing an influx into the motor neuron
3. Acetylcholine released
4. Acetylcholine diffuses across synaptic cleft
5. ACH binds to ACH receptors on post-synaptic membrane and opens channels (ligand-gated sodium channels)
6. Acetylcholine broken down by acetylcholinsterase
Synaptic cleft
Space between presynaptic terminal in motor neuron and postsynaptic membrane (skeletal muscle) in which acetylcholine diffuses across
Botulism
Blocks ACH release at neuromuscular junction
Cobratoxin
Blocks ACH receptors at neuromuscular junction on ligand-gated sodium channels in postsynaptic membrane
Curare
Blocks ACH receptors at neuromuscular junction on ligand-gated sodium channels in postsynaptic membrane
Nerve gas (sarin)
Blocks acetylcholinesterase (harmful at neuromuscular junction)
Black Widow Toxin
Makes pores in motor neuron membrane at neuromuscular junction
Acetylcholine Action and Location
Excitatory to skeletal muscles; excitatory or inhibitory at neurons
Central NS, Peripheral NS, Neuromuscular junction
ACH can cause 2 different effects
This is due to two different receptors that bind ACH
Muscarine
ACH receptor that slows heartbeat
Inhibited by atropine
Nicotine
ACH receptor that causes muscle contraction
Inhibited by curare
Norepinephrine Action and Location
Excitatory or Inhibitory*
Central NS, Peripheral NS
Glutamate Action and Location
Excitatory*
Central NS
GABA Action and Location
Inhibitory*
Central NS
Met-enkephalin Action and Location
Inhibitory
Central NS
Integration of responses within the nervous system can be done by
Different neurotransmitters released by multiple presynaptic neurons causing varied responses in postsynaptic neuron
How do action potentials cause diversity of actions
- Frequency of action potentials
- A neuron may go to different locations and alter function in multiple other neurons
- Multiple neurotransmitters in different neurons (although, single neuron, single neurotransmitter)
- A single neurotransmitter can bind to different receptors
- Multitude of responses (IPSP, EPSP) than can alter the membrane potential of a neuron
Invertebrate evolution of nervous system involves
Increasing cephalization (concentration of sense organs, nervous control, etc., at the anterior end of the body, forming a head and brain)
Vertebrate evolution of nervous system involves
Increase in body weight corresponds to increase in brain size
Evolutionary trend of brain
Expand, more complex
Although, some of the primitive regions such as the brainstem are similar
Number of neurons in sensory receptors
1x
Number of neurons involved in integration in CNS
200,000x
Number of neurons in effector organs (motor system)
10x
Internal sensory pathways
Blood chemistry, pressure, temperature
Nerves from many internal organs (referred pain)
Input generally goes to medulla and other primitive areas of the brain
Baroreceptors
Monitor blood pressure - provide data on blood pressure to medulla
Carotid artery baroreceptor
Aortic baroreceptor
Carotid arteries
Deliver blood to brain (both sides of neck)
Baroreceptors report to
Medulla oblongata (vasomotor center and cardioinhibitory center)
Carotid artery baroreceptor connects via glossopharyngeal nerve
Aortic baroreceptor connects via vagus nerve
Medulla oblongata acts on
Heart via vagus nerve
Blood vessels via sympathetic neuron
Changes in action potentials in neurons from carotid baroreceptors during differing blood pressures
Carotid sinus nerve impulses increase in frequency with increased blood pressure and impulses decrease in frequency with decreased blood pressure
Cardiovascular center
- In medulla
- regulates blood pressure by feedback circuit to heart and blood vessels
- Sends output to sympathetic neurons to release NE on heart and release epinephrine from Adrenal (increases heart rate and stroke volume -> increases cardiac output and therefore blood pressure; Constricts specific arterioles –> increases resistance and therefore blood pressure)
- Sends output to parasympathetic neurons to release ACH on heart: decreases heart rate and atrial contractility which decreases blood pressure
The sympathetic and parasympathetic nervous system acts on
Smooth muscle
Cardiac muscle
Exocrine muscle
Some endocrine glands
Stimuli in digestive tract acts on
Enteric nervous system, which then acts only on digestive organs
Afferent division
The sensory (afferent) division carries sensory signals by way of afferent nerve fibers from receptors in the central nervous system (CNS)
Efferent division
The efferent or motor division transmits impulses from the CNS out to the peripheral organs to cause an effect or action.
Autonomic nervous system regulates
Visceral activities (circulation, digestion, thermoregulation, pupil size,…)
Most visceral organs are innervated by both sympathetic and parasympathetic nerve fibers (dual innervation)
Two divisions exert opposite effects
Sympathetic system
Preparation for strenuous physical activity in emergency situations
Parasympathetic system
General housekeeping activities in relaxed situations
Parasympathetic postganlionic fibers release
ACH (cholinergic fibers)
Sympathetic postganglionic fibers release
norepinephrine (NE) (adrenergic fibers)
Varicosities
Terminal branches of postganglionic fibers have
varicosities for diffuse release of neurotransmitters
Adrenal medulla
Modified sympathetic ganglion which releases NE and epinephrine into the blood
Which division of the autonomic nervous system has longer preganglionic fibers
Parasympathetic
Cholinergic nicotinic receptors
- On postganglionic cell bodies in all autonomic ganglia
- Open nonspecific cation channels when ACh binds
- More Na enters than K leaves, resulting in depolarization
Cholinergic muscarinic receptors
- On effector cells of parasympathetic systemn
- Five subtypes linked to G proteins that activate second messenger systems when ACh binds
5 dfferent types of muscarinic receptors
M1, M2, M3, M4, M5
The muscarinic agonists cause receptor activation; the antagonists produce receptor blockade
Thoracolumbar sympathetic nerves*
The sympathetic nervous system originates in the thoracolumbar region of the spinal cord. This system is responsible for stimulating fight-or-flight responses in the body, which heighten senses, mobilize energy, and temporarily pause physiological processes like digestion and voiding
Adrenergic receptors
On effector cells of sympathetic system
Epinephrine or NE binding coupled to G proteins
Types of Adrenergic receptors
a1, a2, B1, B2, B3
a1 receptor
bind to NE»_space; E, excitatory response, smooth
muscle of some blood vessels, vasoconstriction (GI tract, kidney)
α2 receptors
bind to NE > E, inhibitory response
β1 receptors
bind equally to epinephrine and NE, excitatory
response – heart, increase heart rate & heart contractility
β2 receptors
bind to epinephrine, inhibitory response – decrease
motility of GI tract, bronchodilation bronchioles of lungs
β3 receptors
binds epinephrine and norepinephrine, stimulatory
response - fat cells, lipolysis
Types of internal sensory input
Baroreceptors
Chemoreceptors
Types of external sensory input
Visual
Touch
Hearing
Smell
