14, 15. The Nervous System Flashcards
Why have a nervous system?
Aids survival, providing a competitive advantage
What are the two types of cells in the nervous system?
🔸 Neurons are excitable cells, they generate and transmit electrical signals called action potentials
🔸Glia or glial cells provide support, nourish and can insulate neurons
What are the five regions of the neuron?
Dendrites, cell body, axon hillock, axon, axon terminals
What is the function of dendrites?
They receive information form other neurons.
What is the function of the cell body?
It contains nucleus and most organelles
What is the function of axon hillock?
Information collated which may lead to axon potentials initiation.
What is the function of axon?
Conducts action potential away from cell body.
What is the function of axon terminals?
Synapse with target cell. Release neurotransmitters
What does the central nervous system consist of?
Brain and spinal cord
What does the peripheral nervous system consist of?
It can be divided into Autonomic nervous system (involuntary) and sensory somatic nervous system (voluntary)
What is the autonomic nervous system broken down into?
Parasympathetic - rest and digest
Sympathetic - Fight or flight
What are the types of glia that insulate neurons?
Oligodendrocytes (CNS) and Schwann cells (PNS) wrap their branch Iike extensions around axons creating a myelin sheath
What is the composition of glia?
Varies by cell types, mostly lipids -fatty white substances
What are afferent neurons?
Afferent neurons (sensory) carry sensory information to the CNS 🔸 their dendrites are found in skin, muscles, organs, etc 🔸 their terminals end in the spinal cord where they connect to interneurons
What are efferent neurons?
Efferent neurons (motor) carry information from the CNS to muscles and organs
🔸Their dendrites are in the spinal cord
🔸Their terminals are found in muscles or organs
What are interneurons?
Enable communication between afferent (sensory) and efferent (motor) neurons and the CNS
What is the function of sensory neurons?
Transducer (convert) physical and chemical stimuli such as light, sound heat pressure smell toast touch into action potentials
How do neurons communicate with each other?
- Neurons generate and transmit electrical signals
- Communication is electrical within the neuron and chemical between neurons and other cell types
- Neurons store energy in the form of an electrical potential difference and use this to transmit an electrical impulse (action potential)
What is an action potential?
The rapid change in charge difference across the nerve cell membrane
What is the resting potential?
When the neuron is not active the membrane potential is at resting potential.
The resting potential changes when ion channels open or close, changing the permeability of the membrane to charged ions.
What is a membrane potential?
Membrane potential is the electrical potential or the charge difference across the membrane, created by Na+, K+ and Cl- ions
Why is the resting potential negative?
In axons, at resting more positive charge outside so more negative charge inside creating charge difference across the membrane (polarised)
-Due to leaky channel, K+ ions move outside in response to the concentration gradient, leading to net negative charge inside
Why is an action potential self regenerating?
It spreads to the adjacent membrane regions in the axon
What are the regions of the synapse?
The presynaptic neuron sends the message
The postsynpatic cell receives the message
What is the process of a nerve impulse?
🔸 The neuromuscular junction is neuron-muscle synapse
🔸 When the action potential arrives at the neuron terminal Na+ ion Chanel’s open, causing depolarisation which caused ca2+ channels to open. Ca2+ ions enter the cell terminal and trigger fusion or a neurotransmitter acetylcholine (ach), vesicles with the presynaptic membrane.
🔸Acetylcholine molecules diffuse across the synaptic cleft and bind to receptors on the postsynaptic membrane
🔸 When receptors on the muscle cell bind Ach, they open and allow Na+ ions to enter which depolarise the postsynaptic membrane.
This can lead to an action potential in the post synaptic cell
What is actetylcholinesterase?
It is an enzyme which degrades Ach and thus switches off the Ach signals. Some medications work by blocking the function of this enzyme so that the stimulus is prolonged.
What sorts of stimulus are detected and why?
🔸 INTEROCEPTION: sensitivity to stimuli originating inside of the body
To maintain a stable internal environment (homeostasis)
🔸 EXTEROCEPTION: sensitivity to stimuli originating outside the body.
So we can plan, react, etc
What is the outer layer of the brain and what is its function?
The outermost layer is known as the cerebral cortex and plays a major role in sensory perception, learning, memory and conscious behaviour
What is the structure of the cerebral cortex?
GYRI-ridges of the cortex
Sulci-valleys of the cortex
What are the four lobes of each cerebral hemisphere?
Frontal lobe, parietal lobe, occipital lobe, temporal lobe
What does the frontal love do?
Diverse functions best described as feeling and planning
What does the parietal lobe do?
Touch and pressure via thalamus
What does the temporal love do?
Recognising, identifying and naming objects
What does the occipital lobe do?
Processes visual information
What are the two language areas of the cortex?
Broca’s area
🔸 frontal lobe
🔸 movement required to produce speech
Wernicke’s area
🔸Parietal and temporal lobe
🔸Understand speech and use of correct words
🔸 involved with sensory more than motor aspects of language
What is aphasia?
Damage to the left hemisphere, where language abilities are localised for 97% of people, can lead to aphasia - a deficit in the ability to use or understand words
What happens when there is damage to either area or the language cortex?
Broca’s area - loss of ability to produce language, broken speech.
Patient is aware, can understand language
Wernicke’s area - inability to understand language - can’t choose correct words to express thoughts
Patient is not aware, can speak clearly but doesn’t make sense
What is sleep?
A period of reduced activity and decreased responsiveness to external stimuli.
What are the two ways in which sleep helps memory and learning?
🔸Helps you focus well during waking hours
🔸Forms neuronal connections (memory) to store newly acquired information while you sleep
What are some effects of sleep deprivation?
- Irritability
- Cognitive impairment
- Memory lapses or loss
- Impaired moral judgement
- Severe yawning
- Hallucinations
- symptoms similar to ADHD
- Impaired immune system
