PSYCH1003
10/07/25
BIOLOCIAL BASES OF BEHAVIOUR
i. Nerve Tissue
Glia cells: support neurons by providing nutrients, clearing waste, and creating
cerebrospinal fluid.
Einstein’s brain had unusually high glial cell density
Linked to brain development and disorders (ALS, Parkinson’s, schizophrenia)
Neurons: cells that receive, integrate, and transmit information
Dendrites: tree-like extensions that receives signals
Soma (cell body): contains the nucleus and produces proteins
Axon: carries electrical impulses away from the soma—can be very long (e.g.,
from spine to toe)
ii. Communication of Neurons
Mylein Sheath: fatty insulation that speeds up signal transmission
Terminal Button: end of axon; releases neurotransmitters
Neurotransmitters: chemical messengers between neurons
Synapse: gap where neurons communicate
iii. The Neural Impulse
Hodgkin & Huxley (1952): used giant squid axon to discover how neurons generate
electrical signals (action potentials)
Neurons contain charged ions inside/outside
Neuron at rest has charge on inside compared to outside
Resting potential: Neuron at rest has a ~-70 mV charge difference
iv. The Neural Impulse: The Action Potential
Stimulation causes ion channels to open briefly
Ion channels: regulates flow of Sodium (N+), Potassium (K+), Calcium (Ca++), and
Chloride (Cl–)
Ion pumps: protein structures which maintain uneven distribution of ions across the
membrane
Sodium channel opens:
Na+ flows into axoplasm (becomes (+) inside)
Self-propagation of depolarization:
, Neural impulse down axon / terminal buttons
Sodium channels close; potassium channels open to restore resting potential
Resting potential restored via K+ channels opening
K+ flows outside membrane
Refractory period
Thus, shift in electrical charge travels along neuron:
The Action Potential
All-or-none law
v. The Synapse Chemicals as Signal Couriers
Synaptic cleft
Presynaptic neuron
Synaptic vesicles release neurotransmitters
Postsynaptic neuron
Receptor sites
“Lock-and-key” method
vi. When a Neurotransmitter Binds: The Postsynaptic Potential
Voltage changes at receptor site–postsynaptic potential (PSP)
Not all-or-none
Changes the probability of the postsynaptic neuron firing
Positive voltage shift – excitatory PSP
Negative voltage shift – inhibitory PSP
Study neuron diagram
vii. Neural Networks
One neuron receives signals from thousands of other neurons – graded potential
Requires integration of signals
EPSPs add up, threshold reached
If IPSPs and EPSPs balance, then neuron remains at rest
Neural networks:
Patterns of neural activity
Interconnected neurons that fire together or sequentially
Synaptic links change
Synaptic pruning
viii. Neurotransmitters
Acetylcholine (ACh)
Motor neurons and voluntary muscles
Agonist: mimics neurotransmitter action
10/07/25
BIOLOCIAL BASES OF BEHAVIOUR
i. Nerve Tissue
Glia cells: support neurons by providing nutrients, clearing waste, and creating
cerebrospinal fluid.
Einstein’s brain had unusually high glial cell density
Linked to brain development and disorders (ALS, Parkinson’s, schizophrenia)
Neurons: cells that receive, integrate, and transmit information
Dendrites: tree-like extensions that receives signals
Soma (cell body): contains the nucleus and produces proteins
Axon: carries electrical impulses away from the soma—can be very long (e.g.,
from spine to toe)
ii. Communication of Neurons
Mylein Sheath: fatty insulation that speeds up signal transmission
Terminal Button: end of axon; releases neurotransmitters
Neurotransmitters: chemical messengers between neurons
Synapse: gap where neurons communicate
iii. The Neural Impulse
Hodgkin & Huxley (1952): used giant squid axon to discover how neurons generate
electrical signals (action potentials)
Neurons contain charged ions inside/outside
Neuron at rest has charge on inside compared to outside
Resting potential: Neuron at rest has a ~-70 mV charge difference
iv. The Neural Impulse: The Action Potential
Stimulation causes ion channels to open briefly
Ion channels: regulates flow of Sodium (N+), Potassium (K+), Calcium (Ca++), and
Chloride (Cl–)
Ion pumps: protein structures which maintain uneven distribution of ions across the
membrane
Sodium channel opens:
Na+ flows into axoplasm (becomes (+) inside)
Self-propagation of depolarization:
, Neural impulse down axon / terminal buttons
Sodium channels close; potassium channels open to restore resting potential
Resting potential restored via K+ channels opening
K+ flows outside membrane
Refractory period
Thus, shift in electrical charge travels along neuron:
The Action Potential
All-or-none law
v. The Synapse Chemicals as Signal Couriers
Synaptic cleft
Presynaptic neuron
Synaptic vesicles release neurotransmitters
Postsynaptic neuron
Receptor sites
“Lock-and-key” method
vi. When a Neurotransmitter Binds: The Postsynaptic Potential
Voltage changes at receptor site–postsynaptic potential (PSP)
Not all-or-none
Changes the probability of the postsynaptic neuron firing
Positive voltage shift – excitatory PSP
Negative voltage shift – inhibitory PSP
Study neuron diagram
vii. Neural Networks
One neuron receives signals from thousands of other neurons – graded potential
Requires integration of signals
EPSPs add up, threshold reached
If IPSPs and EPSPs balance, then neuron remains at rest
Neural networks:
Patterns of neural activity
Interconnected neurons that fire together or sequentially
Synaptic links change
Synaptic pruning
viii. Neurotransmitters
Acetylcholine (ACh)
Motor neurons and voluntary muscles
Agonist: mimics neurotransmitter action
