Nervous System Flashcards
What are the three types of Neurons and their function?
Sensory Neurons (detect), Interneurons (process) and Motor Neurons (respond)
What do Neurons do?
They receive input, conduct action potentials and release neurotransmitters throughout the body.
What do glial cells do?
Support neuron function, form myelin sheath on axons, form blood-brain barrier and provide nutrients, support and waste removal in ECF of brain.
What is the Myelin Sheath?
Causes action potentials to conduct faster down the axon, reduce sodium leaking out
Brain neurons create a complex network with axons that send signals:
From the front to the back of the brain, to neighbouring neurons and from left to right hemisphere and vice versa.
What is the Central Nervous System made of?
The brain and spinal cord (made of neurons and glial cells closely packed together)
What is the Peripheral Nervous System made of?
Peripheral Nerves (made of sensory and motor axons packed together)
What is Sensory Information?
Information is sent from the sensors into peripheral nerves to the spinal cord and brain
What is Motor Information?
Information sent to the spinal cord and brain into peripheral nerves to control muscle
What is transduction?
To convert or change from one form to another
What is sensory transduction?
The conversion of a sensory stimulus into action potentials
How are sensory receptors categorised?
By the type of stimuli they can detect and transduce. (eg. thermoreceptors (temperature), osmoreceptors (osmolarity), chemoreceptors (chemicals), photoreceptors (light), nocioreceptors (pain), mechanoreceptors (pressure, stretch, motion)
What are Somatic Receptors?
They detect stimuli from the external environment
In skin, skeletal muscle and special sensors (eg. nose)
What are Visceral Receptors?
They detect stimuli from the internal environment
In internal organs (viscera), glands and blood vessels
Somatic Sense: Vision
Transduction of light into electricity (action potentials)
Light enters photoreceptors at the back of the eye
Light causes ion shifts inside photoreceptor cells
Creating action potentials, sent to the brain along axons
Brian interpretation = visual images
Somatic Sense: Vestibular
Transduction of motion into electricity
Movement of the head causes deformation of inner ear cells
This allows ions to enter and depolarise the cells
Creating action potentials, sent to the brain along axons
Brain interpretation = head movement and orientation
Somatic Sense: Proprioception (limb muscle)
Transduction of stretch into electricity
Stretch of the sensory neuron endings in muscle, tendon or skin
Physically pulls on the membrane allowing ions to enter neurons
Creating action potentials, sent to the brain along axons
Brain Interpretation = location of each limb in relation to the torso
Visceral Sense: Pressure
Transduction of pressure: Baroreceptors transduce pressure changes into action potentials
Pressure deforms membrane, allowing ions to move, leads to depolarisation
Action potentials are sent to the brain and/or result in stimulation and contraction/dilation of smooth muscle
Visceral Sense: Blood Osmolarity
Transduction of osmolarity: Osmoreceptors in the hypothalamus transduce osmolarity changes into action potentials
Osmolarity affects certain channels, affecting ion movement and depolarisation
Action potentials are sent to stimulate release of hormones to correct osmolarity changes
Visceral Sense: Blood Acidity (pH)
Transduction of acidity: chemoreceptors transduce changes in blood CO2 and H+ levels in action potentials
CO2 and H+ levels affect various receptors in complex interactions, leading to depolarisation
Action potentials are sent to respiratory control neurons in the brain stem that monitor and control blood acidity
What is a sensory unit?
Nerve endings and the sensory neuron they attach to
What is a receptive field?
The area of detection where nerve endings are.
Areas of the skin with large, widely spread receptive fields detect less detail (eg. arms and legs).
Areas of the skin with small, closely packed receptive fields can detect more detail (eg. fingertips and lips)
Receptive Fields and the Somatotopic Map
Body parts with more sensory neurons = more representation in the brain.
1 sensory neuron per receptive field.
Simulus Intensity
Mild stimuli cause few action potentials
Intense stimuli cause many action potentials
Fast Adapting Receptors (eg. thermoreceptors)
Send action potentials when change is detected
Stop sending if stimulus is non-threatening
Less intensity or no more sensation
Slow Adapting Receptors (eg. pain receptors)
Send action potentials the entire time a threatening stimulus is present
Constant sensation or increased intensity if more receptors get activated
Left Brain
Receives sensory input from, and sends motor control signals to the right side of the body
Analytic thought, logic, language, science and math
Right Brain
Receives sensory input from, and sends motor control signals to the left side of the body
Holistic thought, intuition, creativity, art and music
Outer Brain - Cortex
Cortex is made of neuron cell bodies, grouped according to function
Neurons involved in awareness, thinking and voluntary control
Inner Brain - Nuclei
Groups of neuron cell bodies in the centre of the brain are called nuclei, grouped according to function
Neurons involved in emotions, memory and involuntary control
The thalamus is our gateway sensory nuclei
Function of the Brainstem
All communication signals between brain and spinal cord pass through.
Brainstem neurons control autonomic function of internal organs (eg. heart rate, BP, Breathing etc.)
Three parts: Mid Brain, Pons, Medulla Oblongata
Function of the Cerebellum
Monitors sensory input to maintain balance and posture
Helps coordinate movements
Stores movement patterns (motor programs eg. walking)
Function of the Basal Nuclei
Selects and maintains desired movement
Eliminates unwanted movement
Regulate muscle tone
Monitor and coordinate sustained contractions (e.g posture)
Control autonomic movement
Function of the Thalamus
Sensory information ‘gateway’ to the brain
Sensory neurons from the body synapse with other neurons, whose axon terminals end up in the primary sensory cortex
Function of the Hypothalamus
Monitors chemicals in blood
Monitors and controls core body temperature, plasma osmolarity, heart rate, blood pressure
Monitors and controls hormones in blood
What is the Primary Somatosensory Cortex?
Somatic sensory signals pass through the thalamus and then to the somatosensory cortex neurons
What is the Primary Motor Cortex?
Cell bodies of primary motor neurons form the primary motor cortex
Action potentials from these neurons go down the spinal cord to stimulate lower motor neurons to activate skeletal muscle
What is Neuroplasticity?
The brain’s ability to reorganise and reform itself by forming new and stronger neural connections (learning and memory)
How does the brain change so we can learn and remember? (3)
- Chemical: increase amount of neurotransmitters released (short term memory)
- Connections: increase number of connections between neurons (long term memory)
- Excitability: neurons become more excitable the more you use them
Describe Brain damage (concusion)
- Hit head and brain bounces against the skull
- Difficulty thinking and remembering, headaches etc.
- Rest, avoid further risk and alcohol/drugs
- Mild (full and quick recovery), More severe (days, weeks or more)
7 ways to increase Brain Health
- Exercise
- Develop Healthy Relationships
- Get enough quality sleep
- Learn new and difficult things
- Healthy diet
- Avoid or reduce alcohol and drugs
- Develop a positive outlook
What are the 3 stages of motor learning and skill development?
Cognitive stage (beginner)
Associative stage
Autonomous stage (elite)
What areas of the brain are involved in movement control?
Frontal lobe, basal nuclei and cerebellum
Final phases of movement initiation (3)
- Upper motor neurons send action potentials
- To lower motor neurons, which send action potentials
- To skeletal muscle
What are lower motor neurons?
‘The final common pathway’ because its the only pathway to the specific muscle fibres it innervates
What events are involved in a reaction time? (4)
- Transduce a stimulus into an action potential
- Send signals to and within the brain
- Send signals to activate muscle
- Create and cycle cross-bridges to contract muscle and move bones
What’s a Reflex?
Sensory input to spinal cord with immediate motor response, no brain control is needed.
Whats the Stretch Reflex?
The muscle spindle gets stretched which causes action potential along sensory neuron to spinal cord. Excitatory synapse with motor neuron from the same muscle group. Causes action potential to stretched muscle which causes it to contract to create ‘reflexive’ movement.
Stimulus: sudden, fast muscle stretch –> Protection: prevent muscle tears
What’s the Golgi Tendon Reflex?
Tendon receptors gets stretched which causes action potential along sensory neuron to spinal cord. Excitatory synapse with interneuron that then inhibits motor neuron and stops activation of muscle, causing it to relax.
Stimulus: muscle developing too much tension and pull on tendon –> Protection: prevents tendon and muscle tears
What’s the Withdrawal Reflex?
Pain receptors activated which causes action potential along sensory neuron to spinal cord. Excitatory synapse with interneurons, one excites motor neuron to innervate flexor muscle, another inhibits motor neuron to prevent innervation of extensor muscle.
Stimulus: contact with damage causing object –> Protection: prevents tissue damage or destruction
What are the autonomic nervous control centres of the brain?
Hypothalamus - parasympathetic (rest or digest), sympathetic (fight or flight)
Brainstem (pons and medulla) - pons (controls medulla neurons or respiratory centre), medulla (nervous involved in many visceral reflexes)
Parasympathetic Innervation
The ‘rest or digest’ system: resting, sleeping, eating
Eye - pupils constrict
Salivary Glands - lots of watery saliva production
Heart - decreased heart rate and blood pressure
Airways to lungs - will narrow, decreased breathing rate
Liver - takes glucose out of the blood and stores it as glycogen
Stomach and Intestines - increased functioning, more digestion, more contraction
Urinary Bladder - contraction of bladder muscle and relaxation of internal sphincter to allow urination
Sex organs - vasodilation to increase blood supply for erection of penis and clitoris; activation of lubrication glands
Sympathetic Innervation
The ‘fight or flight’ system: fear-based response, stress, exercise
Eye - pupil dilation
Salivary Glands - thicker, less watery saliva production
Heart - increase heart rate and blood pressure
Airways to lungs - will widen, increased breathing rate
Liver - creates more glucose and releases it into the blood
Stomach and Intestines - less function, less digestion, less contraction
Urinary bladder - relaxing of bladder muscle and constriction of internal sphincter to prevent urination
Sex organs - less lubrication; decreased blood supply, loss of penile and clitoral erection
Sweat glands - sweat production
Blood Vessels - primarily vasoconstriction. some vasodilation in skeletal muscle
How can the neurons from the parasympathetic and sympathetic systems have such different effects on the same organ?
Parasympathetic releases acetylcholine (ACh)
Sympathetic releases noradrenaline (NA)
How does a reflex provide protection?
Cardiac: adjusts heart rate
Vasomotor: maintains blood pressure
Swallowing: ensures nutrient intake
Coughing: keeps airways open
Respiratory: adjusts breathing rate
What is the enteric nervous system?
In smooth muscle of the gastrointestinal tract. Causes contractions when stretched or stimulated by chemicals from food.
What is gut microbiome?
Trillions of bacteria and other microbes in the gut which creates chemicals that feed back and influence the brain.
In regards to the microbe-gut-brain axis, what do the parasympathetic and sympathetic nerves influence? (4)
Mobility
Secretions
Supply of nutrients
Balance of the gut microbiome
In regards to the microbe-gut-brain axis, what do the sensory enteric nerves and gut microbes influence? (4)
Neurotransmitters
Stress/anxiety and depression
Humour and behaviour
Immune system
Imbalance of the gut microbes can cause:
Mood disorders and pain
Allergies, metabolic and auto-immune diseases
Reduced mental focus, memory and learning
What are the two types of ergoreceptors activated in working muscle?
Chemo-receptors (respond to increased levels of waste products from ATP production and use)
Mechano-receptors (respond to stretch and compressive forces created by contraction)
