Exam 2 - Neurons, Sensory, & Reflexes Flashcards
Neurons
Basic unit of the nervous system
Sensory-motor integration
Basic principle of nervous system
Reflexes
The basic unit for sensory-motor integration
Sensory neuron connecting to motor neuron for response
Dendrites
Branches
Major receptor of signals for neuron
Cell body
Also: soma/perikaryon
Process and integrates signals
Emits outgoing signals from neuron
Axon
Major transmitter of signals for neuron
Cytoplasm
Consists of protein molecules in watery substance within membrane
Nucleolus
Centerpiece within nucleus
“Heart within heart”
Nucleus
Heart of neuron
Control center of neuron
Mitochondria
Energy source for cell
Axon hillock
No nissl bodies
Gateway to cell
Area where axon meets cell body
Nissl bodies
Protein synthesis
Not in axon hillock
Axon terminals
Root-like telodendra endings of axon
“Tree roots”
Axon boutons
Also: buttons
Knob on end of axon terminals for presynaptic function
Synaptic vesicles
Within axon boutons
Packets of neurotransmitter substances that release to other neurons or muscles
Myelination
Allows for rapid transmission of neuronal impulses
Schwann cells
Cells that form myelin around axons
Nodes of ranvier
Space between two internodes (segments) of myelin
Nervous system function
Sensory afferent (input) to motor efferent (output)
Sensory info from outside body travels into nervous system by sensory neurons and contacts central nervous system through dorsal horn (in spinal cord and brain stem)
Sensory (afferent) receptors
Exterocepters
Propriocepters
Interocepters
Exterocepters
Receive stimuli on surface of body
Includes: vision, sound, smell, and superficial skin (cutaneous) sensation
Propriocepters
Receive stimuli from muscles, tendons, and joints
Includes inner ear
Not touch, but position in space
Interocepters
Receive stimuli from internal surfaces and include sensations of pain, pressure, or distension (swelling) from smooth muscles, organs, and viscera
Energy transformers
Receive and transform energy based on the type of signals they process
Mechanoreceptive
Chemoreceptive
Thermoreceptive
Nociceptive
Mechanoreceptive
Touch, pressure, and position
Stretch, vibration
Chemoreceptive
Gustatory (taste) and olfaction (smell)
Thermoceptive
Temperature
Nociceptive
Pain receptors for noxious stimuli affecting cells and tissues
Graded potential
Leads to action potential when strong enough
Occurs in dendrites and soma when there is a change in voltage
Spreads in all directions and dies out as it spreads
Action potential
Axon hillock to axon to terminal buttons
Sends impulses for long distances
Excitatory or inhibitory
All or nothing; keeps strength
Generating action potential (1-3)
- Cell membrane polarized @ -70mv; resting membrane potential
- Cell body receiving excitatory and inhibitory signals from other neurons
- Signals depolarize membrane
Generating action potential (4 and 5)
- Axon hillock stimulated; action when graded is strong
5. Action travels down axon with same speed and strength to terminals
Generating action potential (6-8)
- Action continues from channels opening and closing to spread depolarization effect
- When depolarization reaches telodendra, presynaptic cell releases neurochemicals
- Presynaptic cell unresponsive for 0.8 ms
Generating action potential (9 and 10)
- Protein pumps activate and repolarize presynaptic cell
10. Post synaptic cell receives neurotransmitter across synaptic cleft and responds
Basic components of reflex pattern
Sensory receptor/afferent neuron
Lower motor neuron (alpha motor neuron) and muscle fibers it activates
Motor unit
Made up of lower motor neuron and muscle fibers
Lower motor neuron
Also alpha motor neuron and final common pathway for response from nervous system
In ventral horn of brain stem and spinal cord
Motor/efferent information travel
Leaves nervous system by lower motor neuron located in ventral horn (in spinal cord and brain stem)
Basic reflex patterns
Monosynaptic stretch reflex
Polysynaptic reflex arc
Gamma loop
Monosynaptic stretch reflex
Most direct reflex response
- Proprioceptive input (muscle spindle) to dorsal root ganglion into spinal/cranial dorsal horn
- Afferent input directly to lower (alpha) motor neuron in spinal/cranial ventral horn
- LMN sends efferent to muscle fibers
- Muscle moves in quick, unsustained, and phasic pattern
Polysynaptic reflex pattern
Second most direct reflex
- Cutaneous input to dorsal root ganglion
- Afferent connects with interneuron between spinal/cranial dorsal and ventral horns
- Interneuron connects with LMN in spinal/cranial ventral horn
- LMN efferent to muscle fibers
- Muscle moves in quick, unsustained, and phasic pattern
Gamma loop
Indirect reflex
- Cutaneous input into dorsal root ganglion and into spinal/cranial dorsal horn
- Afferent axon connects with gamma motor neuron in spinal/cranial ventral horn
- GMN sends efferent to muscle spindle telling it to stretch
- Muscle spindle stretches
- Stretch causes spindle to send afferent to dorsal root ganglion and into spinal/cranial dorsal horn
- Spindle afferent connects with LMN in spinal/cranial ventral horn
- LMN sends efferent stimulation to muscle fibers
- Muscle moves in relatively sustained pattern
