Physiology Midterm Flashcards
What Nervous system are sensory receptors in? What do they respond to? What do they produce? Where does this product go?
PNS
Respons to stimuli
they produce graded potential that trigger AP along afferent nerve fibres.
Eventually the signal goes to the cortex
How are sensory receptors classified?
Type of stimulus
location within body
complexity of the structure
What are 5 types of stimulus?
Mechanoreceptors thermoreceptors photoreceptors chemoreceptors nociceptors
What are the classifications of sensory recetora based on location?
exteroceptors
interoceptors
proprioceptors
What are the classification based on complexity
simple and complex
What are simple receptors involved in?
How can simple receptors be divided?
touch, pressure, vibration, temperature, pain, proprioception
Free (unencapsulated dendritic endings) & encapsulated dendritic endings
What are examples of free dendritic endings?
Tactile (Merkel cells)
Hair follicle receptors
What are 6 encapsulated dendritic endings?
Tactile (Meissner's corpuscle) lamellar (pacinian) corpuscle Bulbous (ruffini's endings) corpuscle Muscle spindles Golgi tendon organs joint receptors
What are complex one?
sense organs for special senses (vision, smell, etc)
What is the somatosensory system?
Part of the sensory system serving body walls and limbs. receives input from exteroceptors, interoceptors and proprioceptors.
What are the 3 levels of organization within the sensory system?
Receptor level
Circuit Level
Perceptual Level
What happens at the receptor level?
sensory receptors are specialized to respond to specific stimuli when in the receptive field. In response to stimuli a receptor potential is generated and then an AP.
Transduction, occurs which transforms a stimulus into an electrical response. The graded potential spreads to nodes of renvier (voltage gated channels) and AP is produced
What is transduction?
Transduction is when a stimulus is transformed into an electrical response
Which receptors adapt rapidly?
Slowly?
continuous?
Meissners/ Pacinicans
Merkel dics/ Ruffini’s endings
pain receptors and proprioceptors (non adapting)
What do 1st, 2nd and 3rd oder neurons do?
1st: cell bodies=located in ganglia (dorsal or cranial) conduct impulses from sensory receptors to spinal cord/brain stem with 2nd order.
2nd: cell bodies reside in dorsal horn of s.c or medullar nuclei. Transmit to thalamus/cerebellum
3rd: located in thalamus conduct impusles to somatosensory cortex in cerebrum. No 3rd neurons in cerebellum
What are the 3 ascending pathways? where found, termination and 1st synapse?
Spinothalamic: lateral and anterior spinothalamic tracts. Crosses over at the level of the spinal cord. Transmits pain, temperature, corse touch.
Dorsal Column Medial Lemniscal: formed by fasiculus cunatus and gracilis (dorsal white column) and medial lemniscal tracts. Synapses in medulla. Fine touch and conscious proprioception
Spinocerebellar tracts: anterior and posterior spinocerebllar tracts. Subconcious information to cerebellum. coordinates muscle activity
What is the pons?
the bridge between cortex and cerebellum. Inferior to midbrain, and forms anterior wall of 4th ventricle. Axons carry info to and from cerebellum
Where is the medulla ablongata?
What is it responsible for?
from pons to spinal cord. Has a role in the autonomic reflex centre for homeostasis. This includes the cardiovascular system, which controls cardiac and vasomotor centres It also includes the respiratory centre which controls the rate and depth of breathing. Some functions overlap with the hypothalamus which exerts control over most visceral functions by relaying instructions through medulla to effectors.
What is the decussation of pyramids? Where is it located?
The medulla, and it is where the motor neurons cross over
Where is the inferior olivary? what does it do?
It is located in the medulla and it relays proprioceptive information to the cerebellum
Where is the cerebellum? what is it involved with?
located dorsal to the pons and medulla. It protrudes under the occipital lobes of the cerebral hemispheres.
It processes inputs from cerebral cortex, brain stem nuclei and sensory receptors. It is involved with timing and patterns of skeletal muscle contraction
What are cerebellae peduncles?
3 paired fibre tracts that connect the cerebellum to the brain stem
What are the 3 peduncles?
Superior: connects the cerebellum and midbrain. The fibers start in the deep cerebellar nuclei and project to the cerebral motor cortex through the thalamus
Middle: connects pons and cerebellum. It is a one way communication fromn the pons to cerebellar neurons. It informs the cerebellum of voluntary motor activities initiated by the motor cortex
Inferior: connects cerbellum and medulla. It contains afferent tracts. Carries sensory information to cerebellum from muscle proprioceptos and vestibular nuclei of the brain. It is involved in equilibrium and balance
What happens in cerebral processing?
the cortex frontal motor association area indicates intent to initiate action and sends collateral to cerebellum to notify of intention.
-receives proprioceptive information and visual information and equilibrium pathways about body positioning. The cortex then receives information and determines the best way to coordinate force, direction and extent of muscle contraction. Through superior peduncles the cerebellum dispatches blueprints for coordination to the cortex. The output goes to brain stem nuclei which send to the motor neurons of the spinal cord.
What 4 structures protect the brain?
bones
meninges
cerebrospinal fluid
blood brain barrier
What do the meninges consist of and what do they do?
three connective tissue membranes that
- cover and protect the CNS
- Protect blood vessels and enclose venous sinuses
- Contain CSF
- Form partitions within the skull
What is dura mater?
a thick, tough layer that surround the brain. it has 2 layers, the periosteal and the meningeal. Spinal cord only has meningeal
Around the brain these layers are fused except where there is enclose of dural venous sinuses. (where drainage of CFS and blood occurs)
The dura septa anchors the brain in spots and separates different regions
What is arachnoid mater?
The loose covering separated by the dura by the subdura space.
What is the subarachnoid space? Where is it and what it used for?
The subarachnoid space is between the archnoid mater and the pia mater. It is filled with CSF and contains the largest blood vessels that are serving the brain. The arachnoid villi direct the CSF into the dural sinuses.
What is pia mater?
a thin delicate connective tissue and tiny blood vessels that cling tightly to the brain and follows the convolutions
What is CSF?
a liquid cushion that gives buoyancy to the delicate CNS tissue. Has protective, nutrient role. Similar to plasma with fewer proteins. Produced by choroid plexuses.
What are choroid plexuses?
clusters of permeable capillaries enclosed by ependymal cells. Forms CSF which then flows through ventricles. It transports CSF to sinuses and transport tubes and drains the blood out through the jugular vein,.
Explain process of CFS?
- choroid plexus of each ventricle produced CSF
- CSF flows through ventricles and into subarachnoid space via median/lateral apertures
- CFS flows through subarachnoid space
- CSF if absorbed into the dural venous sinuses via the arachnoid villi
What is the blood brain barrier?
A protective mechanism that helps maintain a stable environment for the brain
What is the blood brain barrier produced by?
- continuous epithelium of capilary wall sealed by tight junctions
- thick basil lamina that surrounds the external face of the capillary
- bulbous feet of astrocytes
What is allowed to pass through the blood brain barrier?
glucose, essential amino acids, some electrolytes, fats, fatty acids, oxygen, carbon dioxide, and fat soluble molecules.
Where is the blood brain barrier permeable?
the hypothalamus (near the vomiting centre) The capillaries are porous but ependymal cells are linked by tight junctions
Where is the spinal cord?
the foramen magnum to L1 or L2.
What is the end of the spinal cord?
The conus medullaris
What are 3 ways the spinal cord is important?
- It is a 2 way conduction system
- major reflex centre
- Associated with 31 pairs of spinal nerves
What are cervical and lumbar enlargements used for?
Nerves to supply the upper and lower limbs
What 2 things hold the spinal cord in place?
- Denticulate ligaments: shelves of pia mater along the length of the cord to the bony walls of the vertebral canal
- filum terminale: fibrous extensions of pia mater inferiorly from the conus medullaris to the posterior surface of the coccyx
What is the Cauda Equina?
the lumbar and sacral spinal nerve roots that angel inferiorly for some distance before reaching the exit points
Explain about gray matter of the spinal cord?
It is located internal to white mater in the spinal cord. organized like butterfly wings and paired with ventral and dorsal horns connected by gray commisure. Ventral horns contain cell bodies.
Where is the dorsal root ganglion?
lateral to the spinal cord and contains cell bodies of sensory neurons.
What do axons do from the dorsal root ganglion?
- Travel to higher spinal cord/brain centres
2. synapse with interneurons in the dorsal horns at the level they enter
What is a spinal nerve formed by?
The fusion or dorsal and ventral roots
What is white mater of the spinal cord?
myelenated and unmyelenated fibred used to communicate between different parts of the spinal cord and between the spinal cord and brain.
What are the three directions of white mater fibers in the spinal cord?
Ascending, descending and transverse
What are general properties of the spinal tracts?
- most pathways cross over from one side of the CNS to another (decussate)
- Most consist of a chain of 2 or three neurons
- Most exhibit somatotopy: precise spatial relationships that reflects orderly mapping of the body
- All pathways and tracts are paired. One on each side of the spinal cord or brain
What is a tract?
A connection of axons in the CNS
What is the general function of cerebral cortex? And what part of the brain is it in?
initiates motor function, localized and interprets sensory stimuli and is involved with intellectual and emotional processing. It is divided into motor, sensory and association areas.
It is in the cerebral hemisphere
What is the general function of white matter in the cerebral hemisphere?
Carries information between the cerebral areas and between the cortex and the lower CNS centres. It consists of myelenated Axons
What is the basil nuclei of the cerebral hemispheres?
It is involved with starting and stopping movements. It prevents unnecessary movements and consists of groups of cell bodies (nuclei) located at the base of the brain
What is the general function of the thalamus and where is it located?
It is involved with sorting and editing sensory informatiom that is going to the cerebral cortex. It is also important for connecting motor and sensory areas.
It is located in the Diencephalon
What is the general function of the Hypothalamus? Where is it loacted?
located in the diencephalon
Hypothalamus is the main control centre for the ANS. It also controls body temperature, food intake, thirst, water balance, biological drives and rhythms. It produces hormones and is part of the limbic system (emotional system)
What is the general function of the epithalamus and where is it located?
Location= diencephalon
The epithalamus is involved with sleep wake cycles and the pineal gland produced the hormone melatonin
what is the general function of the midbrain and where is it located?
The midbrain is located in the brain stem. It is a conduction pathway from higher to lower centres. It is connected to craneal nerves
What is the general function of the pons and where is it located?
The pons is located in the brain stem
It is a bridge that is a conduction centre from higher to lower centres. It is connected to craneal nerves and control of vital functions such as respiration, blood pressure etc
What is reticular formation and where is it located?
A functional system located throughout the brainstem. It is involved with cerebral cortical alertness and filters repetitive stimuli. It is involved in some muscle contractions.
What is the general function and location of the cerebellum?
It coordinates muscle contractions and receives proprioceptive information as well as motor intentions. It integrates the sensory and motor information to create smooth movement.
What are tactile merkel discs cells?
Free endings are enlarged, disc shaped epidermal cells. They lie in the basil layer of the skin epidermis (light touch receptors)
What are hair follicle receptors?
Dendritic endings wrapped around hair follicles. They are free and are light touch receptors. Ex; they detect the bending of hair when a mosquito is nearby
What is a tactile (meissners) corpuscle?
encapsulated. Found in derman papillae and numerous in sensitive and hairless skin (ex fingertips, soles of feet) These receptors are used for discriminating touch