Divisions of the nervous system

• What are the two parts of the nervous system?

  • CNS (central)
  • PNS (peripheral)
• What does the CNS encompass?

  • Spinal cord
  • Column of nerves between PNS + brain
  • Relay neurons
  • Brain stem
  • Connects brain + spinal cord
  • Pons + medulla
  • Brain
  • Interprets + stores info
  • Gives orders to glands/organs/muscles
  • Divides into 3 parts
  • Motor neurons
• What are the 3 divisions of the brain?

  • Forebrain
  • Telencephalon
  • Neocortex
  • Basal Ganglia
  • Limbic system
  • Diencephalon
  • Thalamus
  • Hypothalamus
  • Midbrain
  • Hindbrain
  • Pons
  • Medulla
  • Cerebellum
• What does the PNS encompass?

  • Cranial nerves
  • Spinal nerves
  • Autonomic nervous system (ANS)
  • Somatic nervous system (SNS)
• What is the somatic nervous system?

  • Controls voluntary movement
  • Voluntary skeletal muscles
  • Links brain + spinal cord to skeletal muscles for conscious control/sensory receptors in skin
• What is the autonomic nervous system?

  • Heart muscle, smooth muscle, glands
  • Involuntary movement
  • Sympathetic nervous system
  • Fight or flight
  • Parasympathetic nervous system
  • Rest + digest
• Label the neurons:

  A) motor neuron

  B) relay neuron

  C) conduction

  D) dendrites

  E) cell body

  F) cell body

  G) cell body

  H) dendrites

  I) axon

  J) myelin sheath

  K) axon

  
• What are the 3 types of neuron?

  • Sensory
  • Motor
  • Relay
• What are sensory neurons?

  • Found in multiple places, e.g. eyes, ears, tongue, skin, etc
  • Convert sensory info into nerve impulses
  • Carry nerve impulses from sensory receptors to spinal cord + brain
• What are relay neurons?

  • Between sensory input + motor output
  • Allow sensory neurons + motor neurons to communicate
  • Within either brain or spinal cord
• What are motor neurons?


  • Located in CNS -> project axons outside CNS + directly/indirectly control muscles
  • Form synapses + control contractions
  • Release NTs when stimulated -> bind to receptors = response triggered = muscle movement
  • Axon of motor neuron fires = muscle with synapse contracts -> strength of contraction depends on neuron's axon firing rate
  • Muscle relaxation = inhibition of motor neuron
• What are excitatory neurotransmitters?

  • 'On-switches' -> increase likelihood of excitatory signal sent to postsynaptic cell
• What are inhibitory neurotransmitters?

  • 'Off-switches' -> decrease likelihood of excitatory signal sent to postsynaptic cell
  • Generally responsible for calming mind/body, inducing sleep + filters out unnecessary excitatory signals
• What is the process of synaptic transmission?

  • Action potential reaches axon terminal of presynaptic neuron + triggers vesicles to release NTs (exocytosis)
  • NTs diffuse across synaptic cleft + bind to complementary postsynaptic receptors
  • If overall charge of NTs in postsynaptic neuron is positive, summation is complete + electrical impulse continues along postsynaptic neuron
• What is the endocrine system?

  • System of glands + organs -> uses hormones to regulate + coordinate metabolism, growth, energy levels, etc
  • Pituitary gland = 'master gland'
• What is a gland?

  • Organ that produces one or more hormones directly into bloodstream
• What is a hormone?

  • Chemical messengers travelling in bloodstream that affect growth, metabolism, etc
  • Targets specific structures to alter their function/release other hormones
• How does the endocrine system regulate itself?

  • Hypothalamus controls pituitary gland's hormone release = controls + regulates general endocrine system
• What are the glands within the endocrine system?

  • Pituitary gland
  • Thyroid gland
  • Adrenal gland
  • Pancreas
  • Ovaries
  • Testes
• What does the pituitary gland do?

  • Releases ACTH, TSH, prolactin, FSH, MSH, ADH + oxytocin
  • Consists of anterior + posterior lobes
  • Regulates emotions + contractions during childbirth
• What does the adrenal gland do?

  • Produces adrenaline + noradrenaline
  • Responsible for fight or flight
  • Increases heart rate + blood flow to brain/muscles
  • Releases stored glucose + fats for use in fight or flight
• What do ovaries do?

  • Produce oestrogen, progesterone + testosterone
  • Regulates female reproductive system, menstrual cycle + pregnancy
• What is the fight or flight response?

  • The first of two systems responding to stress
  • Sympathomedullary pathway = body's way of responding to acute stress
  • Acute stressor noticed = hypothalamus activates sympathomedullary pathway to enable body to deal with threat
• What is an acute stressor?

  A sudden, intense, short-term stressor, e.g. an argument or traffic jam
• What is the fight or flight response process?

  • Threat sensed by hypothalamus (CNS) -> alerts ANS
  • Sympathetic nervous system alerted -> releases noradrenaline
  • Noradrenaline travels to organs/glands + begins ForF response
  • Sympathetic adrenomedullary pathway alerted = adrenaline + noradrenaline released
  • Adrenaline travels via bloodstream to organs/glands + continues ForF response
  • Non-vital functions suppressed (e.g. digestion, salivation) -> energy diverted to functions vital to a quick escape/aggression
• What is the sympathetic response at the time of an acute stressor?

  • Sweat produced
  • Pupils dilate
  • Breathing rate increased
  • Salivation ceased
  • Digestion ceased
  • Heart rate increased
• What is the parasympathetic response post-acute stressor?

  • Saliva produced
  • Pupils constrict
  • Heart rate decreased
  • Breathing rate decreased
  • Increased digestion rate
• Who came up with Fight or Flight?

  • Canon
• Fight or flight A&E point 1: makes us aware of possible implications of acute stress + how to address them -> real-life application

  • Acute stressors in modern society = exams, public speaking, etc
  • Today, physiological responses caused by ForF = unhelpful
  • e.g. quickened breathing, higher brain functions shutting down, salivation ceasing, etc
  • Being aware of ForF's changes to the body = people can learn techniques (e.g. breathing/grounding exercises) to calm down + respond appropriately
• Fight or flight A&E point 2: ForF response theory may suffer from gender bias against women -> assumed universality

  • Most research on ForF conducted by/on men -> ignores how women react to threats
  • Taylor et al. (2000) -> women = 'tend and befriend' (protecting themselves + children through nurturing responses + forming alliances)
  • This may also suffer from alpha gender bias...
  • Likely that both sexes perform a mixture of both ForF and T+B -> both of these areas need to be further researched to remove socialised biases about sex that can interfere with accuracy
• Fight or flight A&E point 3: fight or flight alone may be incomplete

  • Gray (1988) -> first phase of human/animal reaction is not fight or flight, but freeze when put in a stressful situation
  • Freeze response = stopping, looking, listening -> focuses individual's attention to seek new info in order to decide whether ForF is the best response