neurophysiology Flashcards
What is the function of Oligodendrocytes and Schwann cells?
They help to provide the myelin sheath around axons in the CNS and PNS, respectively.
What is the function of astrocytes?
They are a stem cell population in the CNS, involved in ion homeostasis and nutritive functions, secretes neurotransmitters, maintains BBB by inducing tight junctions
What is the function of microglia?
They are the immune cells within the brain for inflammation and repair, involved in phagocytosis
What is the function of ependymal cells?
They are epithelial cells lining the ventricles and separate the cerebrospinal fluid from the nervous tissue. Some ependymal cells have a specialised function within the ventricles as part of the chorus plexus which produces CSF.
Difference between oligodendrocytes and Schwann cells
- oligodendrocytes are found in the CNS while Schwann cells are found in the PNS
- 1 oligodendrocyte myelinates multiple axons while 1 Schwann cell myelinates 1 axon
What are the 3 ascending pathways and their functions and decussations?
1) Spinothalamic System
- Anterior spinothalamic: crude touch, pressure
- Lateral spinothalamic: pain, temperature
- decussates at the spinal segment
2) Dorsal Column Medial Lemniscus System
- fine/discriminative touch, vibration, pressure, proprioception (conscious)
- decussates at medulla from dorsal column to medial lemniscus
3) Spinocerebellar System
- unconscious proprioception
- nerve fibres can cross or not cross midline
What are the descending pathways and their functions?
1) Cortico-spinal tract
- conscious voluntary control of the muscles of the body and face
- decussates at the medulla
2) Extrapyramidal System
- responsible for the involuntary and automatic control of all musculature, such as muscle tone, balance, posture and locomotion
Name the functional areas of the cerebral cortex:
Frontal lobe:
- Pre-central gyrus (motor cortex)
- Pre-frontal cortex (PFC)
- Motor speech (Broca)
Parietal lobe:
- Post-central gyrus (sensory cortex)
Temporal lobe:
- Auditory cortex
- Sensory speech (Wernicke)
Occipital lobe
- Primary & secondary visual cortex (Brodmann)
Homunculi of the brain aspects
Lateral:
Superior:
Medial:
This is referred to as _______
Lateral: Face, Tongue, Hands
Superior: Hands, rest of the body
Medial: Genitalia, Legs, Feet
This is referred to as somatotopic arrangement.
Spaces on myelinated neuron that aren’t myelinated are called ____________. The conduction that takes place here is called ____________.
On non-myelinated neurons, _____________ takes place. Activation of __________________ occurs along the __________________.
Spaces on myelinated neuron that aren’t myelinated are called {{c1::Nodes of Ranvier}}. The conduction that takes place here is called {{c1::saltatory conduction}}.
On non-myelinated neurons, {{c1::continuous conduction}} takes place. Activation of {{c1::voltage-gated sodium channels}} occurs along the {{c1::entire length of the neuron}}.
Summarise the UMN/LMN lesions in parts of the CNS
Brain Lesions (what kind of lesion, affects what)
1. Cerebral hemispheres: {{c1::UMN, contralateral}}
2. Brain stem: {{c1::UMN, contralateral +/- ipsilateral face}}
3. Cerebellum does not contain UMN/ LMN, but lesions here can cause {{c1::pure ataxia at ipsilateral side}}
-> Brain lesions tend to produce unilateral signs.
Cord Lesions
4. Cervical spinal cord: {{c1::UMN/LMN, 4 limbs}}
5. Thoracic spinal cord: {{c1::UMN/LMN, legs}}
6. Lumbosacral spinal cord: {{c1::UMN/LMN, legs}}
-> Cord lesions tend to produce bilateral UMN signs.
Consequences of LMN lesion
Hypotonia - flaccid paralysis (loss of muscle tone)
Muscular atrophy
Areflexia (absent reflexes)
Consequences of UMN lesion
Hypertonia - rigid paralysis (increased muscle tone)
Hyperactive reflexes
The opening of which channel will lead to the initiation of action potentials?
voltage-gated Na+ channel (higher conc. of Na+ outside cell would cause Na+ to ENTER the cell causing depolarisation)
