CNS/Sensory&Cognitive/Motor Flashcards
Motor output:
-from where to where?
-cell bodies where?
-From CNS to effectors
-Cell bodies in CNS
Sensory input:
- what 2 types of sensory?
-from where to where?
-cell bodies where?
-somatic and visceral sensory
-From receptors to CNS
-Cell bodies out of CNS
Somatic efferent:
-innervates what?
-type of neurons?
-innervates skeletal muscles
-only excitatory (Ach) neurons (motor neurons)
Autonomic efferent:
-innervates what?
-type of neurons?
-innervates interneurons, smooth and cardiac muscles
-excitatory and inhibitory neurons
Spinal nerves:
-2 types of sensations and where do they come from?
Somatic sensation:
comes from the receptors of the eyes, ears, nose, tongue and skin
Visceral sensation: comes from the internal organs
Brainstem:
3 parts?
Midbrain
Pons
Medulla
White matter vs gray matter:
-brain vs spinal cord
Brain: white matter inside and gray matter on the outside
Spinal cord: white matter outside and gray matter on the inside
What do the cervical nerves innervate? (4)
How many pairs?
Neck
shoulders
arms
hands
8 pairs
What do the Thoracic nerves innervate? (3)
How many pairs?
shoulders
chest
upper abdominal wall
12 pairs
What do the lumbar nerves innervate? (3)
How many pairs?
Lower abdominal wall
hips
legs
5 pairs
What do the sacral nerves innervate? (2)
How many pairs?
genitals
lower digestive track
5 pairs
How many pairs in the Coccygeal nerves?
1 pair
What enters the dorsal horn?
afferent sensory info
What exits the ventral horn?
efferent motor control neurons
The spinal nerve approaches the spinal segments and divides into 2….divides into what and what?
divides into:
dorsal root
ventral root
What does the dorsal root ganglia contain?
cell bodies of the afferents sending sensory info into the spinal cord
10 of the 12 cranial nerves connect to the ___________. Cranial nerves have both ___________ and ____________ signals together.
brain stem
sensory
motor
What is a concussion, and why is it a concern in terms of brain swelling?
A concussion is a form of bleeding or swelling in the brain. The concern with a concussion is that excessive brain swelling can lead to increased pressure within the hard skull, potentially pushing the brain out of the base of the skull.
Why is the location of the cranial nerves involved in the pupillary reflex significant in the context of head injuries?
The location of these cranial nerves is significant because they exit the brain stem at the base of the skull. In cases of brain edema, swelling, or bleeding inside the brain, the brain’s expansion can compress these nerves, impacting the pupillary reflex.
Early development of the nervous system
Fertilized egg (ovum)
Ball of cells
Blastocyst - week1
Blastocyst - week 2 (+ definition)
Blastocyst - week 3 (embryonic disk
Embryonic disk becomes ectoderm, mesoderm and endoderm.
Formation of neural groove
Formation of neural tube - week 4
Neural tube – vesicles
become what ?(4)
Forebrain:
Cerebral hemispheres+thalamus
Midbrain:
midbrain
Hindbrain:
cerebellum+pons+medulla
Straight portion:
spinal cord
Cavity:
ventricles+central canal
Ectoderm becomes? (2)
-neural groove (neural tube)
-nervous system (CNS and PNS)
Mesoderm becomes? (2)
-muscles and various other body parts start to develop
-the dura
Endoderm becomes? (1)
digestive system
Choroid plexus:
what is it?
what does it do?
-fuzzy lining on the ventricles
-where CSF is produced
What is the primary source of production for cerebrospinal fluid (CSF)? (how much vs how much ventricles contain)
primarily produced by the choroid plexus, mainly in the two lateral ventricles, at a rate of approximately 500 ml per day (Ventricles contain 150mL).
Name three functions of cerebrospinal fluid (CSF) in the central nervous system (CNS)
- Supports and cushions the CNS.
- Provides nourishment to the brain.
- Removes metabolic waste through absorption at the arachnoid villi.
What is the composition of cerebrospinal fluid (CSF) in terms of its appearance and notable components? (5)
-sterile
-colorless
-acellular.
-It contains glucose
- has a specific gravity equal to that of the brain.
How does cerebrospinal fluid (CSF) circulate within the central nervous system?
Cerebrospinal fluid circulates passively and is not actively pumped.
Explain the CSF circulation steps. (10)
- Choroid plexus
- Lateral ventricles
- intraventricular Foramens (Foramen of Monro)
- Third ventricle
- Fourth ventricle
- Foramen of Lushka & Foramen of Magendie
- Subarachnoid space
- Arachnoid villi
- Dural sinus
- Venous system
What are the 3 meninges of the CNS?
Dura mater: The outermost and toughest layer, the dura mater, provides protection and support for the brain and spinal cord. It is a thick, durable membrane that surrounds the CNS.
Arachnoid membrane: The middle layer, the arachnoid mater, is a thin and delicate membrane that lies beneath the dura mater. It helps cushion the CNS and contains cerebrospinal fluid (CSF), which circulates around the brain and spinal cord.
Pia mater: The innermost layer, the pia mater, is a thin, vascular membrane that directly adheres to the surface of the brain and spinal cord. It provides nutrients to the nervous tissue and is closely connected to the underlying neural structures. Contains Trabeculae, that are thin, connective tissue strands that extend from the pia mater into the underlying neural tissue, providing structural support and anchoring the pia mater to the CNS.
Where does CSF return to the blood?
Dural sinus
What is supplied to the brain by the blood?
-Glucose is usually the only substrate metabolized by the brain.
-Very little glycogen in the brain.
–Brain needs a continuous supply of glucose and oxygen (glucose transport into the brain does not require insulin).
A few seconds of blood supply interruption can lead to…
and a few minutes…
loss of consciousness
neuronal death (stroke)
How much blood % does brain receive?
Brain receives 15% of total blood (but is 2% of total mass)
Explain the circle of Willis.
The aorta branches into the common carotid which branches into internal carotids. Behind the internal carotids, we have the vertebral arteries, that join to make the basilar artery. They all join to form the circle of Willis. This acts as a safety factor, which means that if one of your internal carotid arteries or the vascular artery or something is blocked and not providing enough blood, this allows blood from the functioning side to be shunt over because you have to keep the blood flow to your brain.
What is the blood-brain barrier, and why is it significant for drug delivery to the brain?
The blood-brain barrier is a protective mechanism in the central nervous system that limits the passage of substances from the blood into the brain. It is crucial for drug delivery because it regulates which substances can enter the brain, impacting the efficacy of medications.
How do the endothelial cells in the central nervous system differ from those in other parts of the body?
Endothelial cells in the central nervous system have tight junctions, which make them impermeable to most substances. This is in contrast to endothelial cells in other parts of the body, which typically have openings or junctions allowing substances to flow through.
What role do astrocytes play in the blood-brain barrier?
Astrocytes are glial cells that help induce the tight junctions between endothelial cells in the blood-brain barrier. They provide structural support and assist in regulating ionic concentrations and maintaining an environment suitable for proper neuronal function.
In addition, Astrocytes, a type of glial cell, provide structural support, regulate ionic concentrations, and maintain a suitable environment for neurons to function correctly in the central nervous system.
How can substances cross the blood-brain barrier?
by being lipid-soluble
passive diffusion or active transport
Name some examples of lipid-soluble substances that can easily cross the blood-brain barrier.
water, oxygen, carbon dioxide, caffeine, and alcohol.
Why does morphine cross the blood-brain barrier slowly, while heroin, derived from morphine, can enter the CNS more rapidly?
Morphine crosses the blood-brain barrier slowly due to its limited lipid solubility. Heroin is chemically modified to enhance its ability to cross the barrier and then reverts to morphine once inside the CNS, preventing it from exiting.
What challenges does the blood-brain barrier pose for drug delivery to the central nervous system?
The blood-brain barrier makes it difficult for drugs to reach the brain, which can be a challenge in treating conditions like brain cancer or infections. Ions and large protein molecules typically do not pass the barrier unless actively transported.
What substances are actively transported into the brain across the blood-brain barrier?
Glucose and specific amino acids are actively transported into the brain through the blood-brain barrier.
What is the difference between sensation and perception?
Sensation is the awareness of sensory stimulation, while perception is the understanding of the meaning of a sensation.
Do we directly perceive the “energy” of a sensory stimulus?
No, we do not directly perceive the “energy” of a sensory stimulus. Instead, we perceive the neural activity that is produced by sensory stimulation.
What is the Law of Specific Nerve Energies?
The Law of Specific Nerve Energies states that regardless of how a sensory receptor is activated, the sensation felt corresponds to what the receptor is specialized for. For example, rubbing your eyes hard can lead to the sensation of seeing light.
What is the Law of Projection in sensory perception?
The Law of Projection states that regardless of where in the brain you stimulate a sensory pathway, the sensation is always felt at the sensory receptor’s location. For example, when Penfield electrically stimulated the somatic sensory cortex, patients perceived somatic sensations in their body.
Can you provide an example of the Law of Projection in action?
An example of the Law of Projection is phantom limb pain after amputation. Even though the limb is no longer present, the sensation is still felt as if it were, illustrating how sensory perception can project sensations to their original location.
What is meant by the term “modality” in sensory perception?
Modality refers to the general class of a stimulus. It describes the type or category of sensory input, such as vision, hearing, touch, taste, or smell.
What does the term “labeled-line” mean in the context of sensory perception?
In a labeled-line system, the brain “knows” the modality and location of every sensory afferent. Each sensory pathway is specifically labeled to convey information about the type of stimulus and where it is coming from.
What are sensory receptors?
Sensory receptors are specialized cells or structures in the body that detect and respond to a precise/adequate sensory stimuli.
What is transduction in the context of sensory perception?
Transduction is the process by which sensory receptors convert stimulus energy into neural activity by the opening and closing of ion channels, that can be transmitted to the brain for interpretation.
What are afferents in the context of sensory perception?
Afferents are nerve fibers or neurons that transmit sensory information from the sensory receptors to the central nervous system.
How does the intensity of a sensory stimulus affect the afferent response?
By determining the magnitude of the receptor potential (stimulus gets stronger and potential gets stronger), which in turn affects the frequency of action potentials generated in the sensory neuron, which will affect the magnitude of neurotransmitter release
What is adaptation in the context of afferent responses?
Adaptation is the process by which afferent sensory neurons change their response to a stimulus over time, either by decreasing or increasing their activity.
Why do the majority of afferents show adaptation?
Most afferent neurons exhibit adaptation to enable us to be sensitive to changes in sensory input. It helps filter out continuous or unchanging stimuli, allowing the sensory system to focus on new or evolving information.
What is the role of non-adapting afferents?
Non-adapting afferents encode stimulus intensity and slow changes. They provide a constant representation of the stimulus and do not reduce their response over time.
What do slowly adapting afferents respond to?
Slowly adapting afferents respond to some stimulus intensity and make moderate changes in the stimulus.
What is the characteristic of rapidly adapting afferents?
Rapidly adapting afferents are specialized to detect fast stimulus changes. They quickly decrease their response to a continuous or unchanging stimulus but rapidly increase their activity when the stimulus changes.
What is a Receptive field (RF)?
The region in space that activates a sensory receptor or neuron.
How do receptive fields of sensory neurons typically relate to one another?
Receptive fields often overlap, meaning they cover adjacent areas in sensory space.
Overlapping receptive fields allow sensory neurons to produce a population code.
What does overlapping receptive fields contribute to in sensory processing?
Overlapping receptive fields contribute to the generation of a population code, where the combined activity of multiple neurons encodes complex sensory information.
What is stimulus acuity, and how does receptive field size relate to it?
Stimulus acuity is the ability to differentiate one stimulus from another. Smaller receptive fields are associated with higher acuity, as they provide more precise information about the location and properties of stimuli.
How does lateral inhibition sharpen sensory acuity?
Lateral inhibition is a neural mechanism where the activity of one neuron inhibits the activity of neighboring neurons. This mechanism sharpens sensory acuity by enhancing the contrast between activated and non-activated neurons in response to a stimulus.
How do descending pathways influence sensory inputs in the nervous system?
Descending pathways are neural pathways that modulate sensory inputs. They provide “top-down” control, allowing higher brain regions to influence and shape sensory information processing, in addition to the “bottom-up” processing from sensory receptors.
What are the key features of touch receptors in the superficial layers of the skin? (2)
Touch receptors in the superficial layers include:
-Merkel disks (slowly adapting, pressure and texture) and
-Meissner’s corpuscles (rapidly adapting, light stroking and fluttering).
What are the key features of touch receptors in the deep layers of the skin? (2)
Touch receptors in the deep layers include
-Pacinian corpuscles (rapidly adapting, strong vibrations) and
-Ruffini endings (slowly adapting, stretch, and bending of the skin, shape of an object).
How do proprioceptors, such as muscle spindles, contribute to somatic sensation? (function)
Proprioceptors, like muscle spindles, provide a sense of the static position and movement of limbs and the body. They help us maintain balance and control our movements.
How do thermoreceptors respond to temperature variations, and what are the temperature ranges they detect?
Thermoreceptors are free nerve endings containing ion channels. Cold afferents respond to temperatures between 0°C and 35°C, while warm afferents respond to temperatures between 30°C and 50°C. Extreme temperatures activate pain receptors.
What are nociceptors, and how do they respond to different types of stimuli?
Nociceptors are free nerve endings that respond to intense mechanical deformation, excessive temperature, or chemicals. They are highly modulated, both enhanced and suppressed, to regulate pain perception.
What activates visceral pain receptors?
Visceral pain receptors are activated by inflammation.
Explain the enhancement of nociceptors leading to hyperalgesia.
- Damaged cells
- Nociceptors send AP to spinal cord.
- Substance P is released in spinal cord
- Enhancement of surrounding nociceptors by injured tissue (chemicals) & afferent feedback onto mast cells which will release histamine
- Dilation of nearby blood vessels
What is hyperalgesia?
an increased sensitivity to pain
What are the primary sensory modalities carried by the dorsal column pathway?
touch and proprioception.
Describe the steps of the dorsal column pathway from the receptors to the cortex.
- Receptors
- Spinal nerve– through the dorsal root ganglion
- Signals ascend the spinal cord via the dorsal columns (ipsilateral)
- Synapse in the medulla (ipsilateral)
- Crosses the midline
- synapse in thalamus (Contralateral)
- Project to somatosensory cortex (Contralateral)
Describe the steps of the Anterolateral pathway from the peripheral receptors to the cortex.
- Receptors
- Spinal nerve– through the dorsal root ganglion
- Signals enter the spinal cord, in the gray matter (dorsal horn) (ipsilateral)
- Synapse in the spinal segment (gray matter) (ipsilateral)
- Cross mid-line at the central canal
- Signals ascend through the anterolateral column (Contralateral)
- Branches into the reticular formation
- Synapse in the thalamus (Contralateral)
- Project to somatosensory cortex (Contralateral)
What is a somatotopic map in the context of the brain? (+which body parts from lateral to medial)
A somatotopic map is a representation of the body’s surface on the cortex, where different areas of the brain correspond to specific body parts. Each body part is mapped to a specific location in the brain.
On a contralateral representation of somatosensory cortex, from lateral to medial: Head, arms, legs
How are mechanoreceptors activated?
By stretching the cytoskeleton strands. They are open by the cytoskeleton strands that connect the ion channels that are in the membrane of the the nerve ending.
What is referred pain due to?
Visceral & somatic pain afferents commonly synapse on the same neurons in the spinal cord.
The spinal segment doesn’t know which afferent is driving the pain. Brain usually assigns it to the skin (somatic afferent).
Explain the Descending pathways that regulate nociceptive information
(analgesia)
It is a top down mechanism.
The afferent drives the info through the anterolateral pathway (contralateral). But there is a neuron starting in the Periaqueductal gray matter (midbrain), then synapsing in the Reticular formation (medulla), following the Dorsolateral funiculus, allowing to inhibit the synapse of the afferent in the dorsal horn. This allows to reduce the release of substance P, and shut off the perception of pain.
Analgesia stops the release of substance P thanks to…
Opiate neurotransmitters
(presynaptic inhibition)
In the eye, what is the fovea centralis?
highest visual acuity
In the eye, what is the optic disk?
blind spot
In the eye, what is the sclera?
white portion of eye
What is the primary function of a lens in the eye?
A lens refracts (bends) light to a single point, aiding in focusing light onto the retina for clear vision.
Which eye structures are responsible for the refraction of light?
Light is refracted by both the cornea and lens to facilitate proper vision.
the cornea or the lens, which structure refracts light to a greater degree?
The cornea refracts light more significantly than the lens.
What happens during accommodation for near vision?
Accommodation for near vision involves adjusting the lens shape via the ciliary muscles
What is myopia? Corrected?
Myopia (nearsightedness) results in difficulty seeing distant objects. Corrected with divergent lens.
What is hyperopia? Corrected?
hyperopia (farsightedness) causes trouble focusing on close objects. Corrected with convergent lens.
