smooth muscle contraction is SLOWER and requires less energy.
the lowering of the sarcoplasmic calcium level causes the dissociation of the calmodulin-calcium complex causing the deactivation of the
myosin light chain kinase.
The resulting dephosphorylation of myosin light chains catalyzed by the enzyme myosin phosphatase masks the myosin binding sites for
actin and leads to muscle relaxation.
CARDIAC MUSCLE
Cardiac muscle displays structural and functional characteristics intermediate between those of skeletal muscle and visceral muscle.
It is found in the HEART and in the PULMONARY VEINS (where they join the heart). It derives from the splanchnic mesenchyme, whose
cells give rise to the EPICARDIUM (external lining of the heart) and the MYOCARDIUM.
The adult myocardium is an anastomised network of cardiac muscle cells that bifurcate into layers (LAMINAS).
Cardiac tissue is characterized by an intrinsic rhythmicity and an ability to contract spontaneously.
cardiac muscle cells are cells:
- medium large
- voluminous, sometimes binucleate
- form end-to-end junctions between cells themselves, called INTERCALARY DISCS
The action potential of cardiac muscle cells is activated by an abundant presence of fast sodium channels, which open and close
quickly. They also have calcium-sodium channels (slow sodium channels) which help keep the calcium concentration high.
contraction. Sarcomeres are present as in skeletal muscle
• Ca2+ also enters the heart muscle from the T tubules
• The T-tubules are more enlarged, and the sarcoplasmic reticulum is more narrow
The spiral arrangement of the ventricular muscle allows the ventricular contraction to push blood up from the apex of the heart. The
interlayer discs contain:
- desmosomes that allow the transfer of force from cell to cell.
- Gap junctions allow electrical signals to pass rapidly from cell to cell.
impulse transmission. The original electrical signals are generated by specialized myocardial cells: PACEMAKER SYSTEM.
Sino-atrial node (SA): it is the primary pacemaker with the greatest automatism. It is located in the right atrium at the level of the outlet of the
superior vena cava. It is capable of generating 70-90 action potentials per minute.
Atrioventricular (AV) node: This is the secondary pacemaker capable of generating 40-60 action potentials per minute.
Purkinje fibers: is capable of generating 35 action potentials per minute.
4. NERVOUS TISSUE
The nervous system provides sensations on the internal and external environment, Integrates sensory information, Coordinates voluntary
and involuntary activities, Regulates and controls peripheral structures and apparatuses, It is the seat of cognition, emotions, memory
The nervous system is organized into the central nervous system (CNS) and peripheral nervous system (PNS).
CENTRAL NERVOUS SYSTEM
– Brain (enclosed in the skull)
– Spinal cord (enclosed in the spinal canal)
SISTEMA NERVOSO PERIFERICO
– Nervi (fasci di fibre nervose)
– Gangli (gruppi di corpi cellulari)
– Sistema nervoso enterico (associato al tubo digerente)
The nervous system develops from the embryonic ectoderm.
It is composed of a communicating network of specialized cells called NEURONS (capable of receiving, processing and responding to
stimuli), which represent the majority:
- of the RECEPTORS
- of the ROUTES OF CONDUCTION
- of the INTEGRATION and ANALYSIS SITES
The functions of the nervous system depend on a property of neurons called EXCITABILITY.
The resting neuron maintains an ion gradient on either side of the plasma membrane, thus creating an ELECTRIC POTENTIAL.
Excitability involves a MODIFICATION of membrane permeability in response to appropriate stimuli as follows:
- the ion gradient is reversed
- the plasma membrane depolarizes
A wave of depolarization, called the ACTION POTENTIAL, spreads along the plasma membrane.
The membrane potential allows the transmission of nerve impulses. The RESTING POTENTIAL is generated by the different composition
and ion concentration in fluids inside and outside the cell
inside the cell
- K+ more concentrated
, - Na+ less concentrated
outside the cell
- K+ less concentrated
- Na+ more concentrated
The depolarization is followed by a repolarization in which the membrane re-establishes its resting potential. At the synapse level,
depolarization determines the RELEASE of chemical substances, the NEUROTRANSMITTERS, which initiate an action potential in the
adjacent neuron.
It does NOT contain extracellular matrix and is made up of two cell types:
NEUROGLIA CELLS: support and protection of neurons
NEURONS: responsible for reception, integration and motor function. Most of the neuron is composed of cell body, multiple dendrites and
SINGLE AXON. The cell body (pyrenophore or soma) represents the central part of the cell (nucleus and cytoplasm). The dendrites branch
off from the pyrenophore, specialized cytoplasmic processes for receiving stimuli from sensory cells and axons (only one). The received
nerve impulses are then transmitted towards the soma.
Each neuron has a single axon which in its final part has an expansion called axon terminal. The axon conducts the impulse in a
centrifugal direction , i.e., carrying the impulse away from the pyrenophore. However, it can receive impulses from other neurons.
The terminal part of the axon are defined TERMINAL BULBS (terminal buttons) and form the SYNAPSES (point of contact between the
various axons)
The cell body, also called SOMA, is the largest region of the neuron. The nucleus occupies a central position and is large, spherical or ovoid
with a clearly visible nucleolus. The cytoplasm of the cell body is rich in mitochondria, RER, especially in motor neurons. There are
numerous polyribosomes, the Nissl bodies.
The region of the cell body from which the axon originates is called the axon mound (or emergence cone), here the trigger area, nerve
impulse generation.
In the soma of neurons, the TIGROID SUBSTANCE formed by RER is distinguished. High protein synthesis. The nucleus is large, with a
developed nucleolus. The extensions are not seen with the traditional markings!!!
With the Golgi method each neuron is colored entirely. The extensions are used to transmit electrical impulses. Extensions are not all the
same. The differences are also functional.
inclusions. MELANIN granules are found in some regions of the CNS (substance nigra, locus ceruleus, 5) and in the sympathetic ganglia of
the PNS.
In the cytoplasm of elderly people we can find LIPOFUSCIN granules. Sometimes it is also possible to find lipid droplets that can represent
a metabolic defect or an energy reserve.
components of the cytoskeleton.
NEUROFIBRILS branch out throughout the cytoplasm of the soma and also extend into extensions.
At the ME it is possible to distinguish:
-MICROTUBULES
-NEUROFILAMENTS
-MICROFILAMENTS (actin): are associated with the plasma membrane
DENDRITE. They represent the SENSORY TERMINALS (afferents) of the neuron and transmit the signal towards the soma. Most neurons
have multiple dendrites, each of which arises from the cell body. Dendrites contain many mitochondria.
The branching and formation of numerous synaptic endings allows the neuron to receive and integrate a multiplicity of impulses.
On their surface there are SPINS that allow synapses to form with other neurons. These spines decrease with aging and poor nutrition.
Cytoplasmic prolongations can be distinguished on the basis of the direction of nerve impulse conduction.
AXON. It originates from the emergence cone of the cell body as a single prolongation extending a much longer distance than a dendrite. In
motor neurons, the axon can be 1 m long. The thickness is proportional to the conduction speed. While the dendrites can be numerous, the
axon can be only ONE, but it can branch producing collaterals, while when it terminates it gives rise to numerous AXON TERMINALS.
The EMERGENCY CONE, a pyramid-shaped region, is generally located opposite the
dendrites.
The INITIAL SEGMENT is represented by the portion between its point of emergence and
the first segment of myelin.
The axolemma of the initial segment presents a thin electron-dense layer, this area, rich in
microtubules and microfilaments, called the TRIGGERING AREA is the region where the
inhibitory and excitatory impulses are added to determine whether or not a
action potential.
The nervous impulse ORIGINS in the CONE OF EMERGENCY and in the INITIAL
STRETCH of the ABSOLEMMA.
The myelinated axons of the CNS and PNS are covered by neuroglial cells which deposit
the myelin sheath which gives it a whitish and translucent appearance, thus allowing the
WHITE substance to be distinguished from the GRAY substance in the CNS.
the lowering of the sarcoplasmic calcium level causes the dissociation of the calmodulin-calcium complex causing the deactivation of the
myosin light chain kinase.
The resulting dephosphorylation of myosin light chains catalyzed by the enzyme myosin phosphatase masks the myosin binding sites for
actin and leads to muscle relaxation.
CARDIAC MUSCLE
Cardiac muscle displays structural and functional characteristics intermediate between those of skeletal muscle and visceral muscle.
It is found in the HEART and in the PULMONARY VEINS (where they join the heart). It derives from the splanchnic mesenchyme, whose
cells give rise to the EPICARDIUM (external lining of the heart) and the MYOCARDIUM.
The adult myocardium is an anastomised network of cardiac muscle cells that bifurcate into layers (LAMINAS).
Cardiac tissue is characterized by an intrinsic rhythmicity and an ability to contract spontaneously.
cardiac muscle cells are cells:
- medium large
- voluminous, sometimes binucleate
- form end-to-end junctions between cells themselves, called INTERCALARY DISCS
The action potential of cardiac muscle cells is activated by an abundant presence of fast sodium channels, which open and close
quickly. They also have calcium-sodium channels (slow sodium channels) which help keep the calcium concentration high.
contraction. Sarcomeres are present as in skeletal muscle
• Ca2+ also enters the heart muscle from the T tubules
• The T-tubules are more enlarged, and the sarcoplasmic reticulum is more narrow
The spiral arrangement of the ventricular muscle allows the ventricular contraction to push blood up from the apex of the heart. The
interlayer discs contain:
- desmosomes that allow the transfer of force from cell to cell.
- Gap junctions allow electrical signals to pass rapidly from cell to cell.
impulse transmission. The original electrical signals are generated by specialized myocardial cells: PACEMAKER SYSTEM.
Sino-atrial node (SA): it is the primary pacemaker with the greatest automatism. It is located in the right atrium at the level of the outlet of the
superior vena cava. It is capable of generating 70-90 action potentials per minute.
Atrioventricular (AV) node: This is the secondary pacemaker capable of generating 40-60 action potentials per minute.
Purkinje fibers: is capable of generating 35 action potentials per minute.
4. NERVOUS TISSUE
The nervous system provides sensations on the internal and external environment, Integrates sensory information, Coordinates voluntary
and involuntary activities, Regulates and controls peripheral structures and apparatuses, It is the seat of cognition, emotions, memory
The nervous system is organized into the central nervous system (CNS) and peripheral nervous system (PNS).
CENTRAL NERVOUS SYSTEM
– Brain (enclosed in the skull)
– Spinal cord (enclosed in the spinal canal)
SISTEMA NERVOSO PERIFERICO
– Nervi (fasci di fibre nervose)
– Gangli (gruppi di corpi cellulari)
– Sistema nervoso enterico (associato al tubo digerente)
The nervous system develops from the embryonic ectoderm.
It is composed of a communicating network of specialized cells called NEURONS (capable of receiving, processing and responding to
stimuli), which represent the majority:
- of the RECEPTORS
- of the ROUTES OF CONDUCTION
- of the INTEGRATION and ANALYSIS SITES
The functions of the nervous system depend on a property of neurons called EXCITABILITY.
The resting neuron maintains an ion gradient on either side of the plasma membrane, thus creating an ELECTRIC POTENTIAL.
Excitability involves a MODIFICATION of membrane permeability in response to appropriate stimuli as follows:
- the ion gradient is reversed
- the plasma membrane depolarizes
A wave of depolarization, called the ACTION POTENTIAL, spreads along the plasma membrane.
The membrane potential allows the transmission of nerve impulses. The RESTING POTENTIAL is generated by the different composition
and ion concentration in fluids inside and outside the cell
inside the cell
- K+ more concentrated
, - Na+ less concentrated
outside the cell
- K+ less concentrated
- Na+ more concentrated
The depolarization is followed by a repolarization in which the membrane re-establishes its resting potential. At the synapse level,
depolarization determines the RELEASE of chemical substances, the NEUROTRANSMITTERS, which initiate an action potential in the
adjacent neuron.
It does NOT contain extracellular matrix and is made up of two cell types:
NEUROGLIA CELLS: support and protection of neurons
NEURONS: responsible for reception, integration and motor function. Most of the neuron is composed of cell body, multiple dendrites and
SINGLE AXON. The cell body (pyrenophore or soma) represents the central part of the cell (nucleus and cytoplasm). The dendrites branch
off from the pyrenophore, specialized cytoplasmic processes for receiving stimuli from sensory cells and axons (only one). The received
nerve impulses are then transmitted towards the soma.
Each neuron has a single axon which in its final part has an expansion called axon terminal. The axon conducts the impulse in a
centrifugal direction , i.e., carrying the impulse away from the pyrenophore. However, it can receive impulses from other neurons.
The terminal part of the axon are defined TERMINAL BULBS (terminal buttons) and form the SYNAPSES (point of contact between the
various axons)
The cell body, also called SOMA, is the largest region of the neuron. The nucleus occupies a central position and is large, spherical or ovoid
with a clearly visible nucleolus. The cytoplasm of the cell body is rich in mitochondria, RER, especially in motor neurons. There are
numerous polyribosomes, the Nissl bodies.
The region of the cell body from which the axon originates is called the axon mound (or emergence cone), here the trigger area, nerve
impulse generation.
In the soma of neurons, the TIGROID SUBSTANCE formed by RER is distinguished. High protein synthesis. The nucleus is large, with a
developed nucleolus. The extensions are not seen with the traditional markings!!!
With the Golgi method each neuron is colored entirely. The extensions are used to transmit electrical impulses. Extensions are not all the
same. The differences are also functional.
inclusions. MELANIN granules are found in some regions of the CNS (substance nigra, locus ceruleus, 5) and in the sympathetic ganglia of
the PNS.
In the cytoplasm of elderly people we can find LIPOFUSCIN granules. Sometimes it is also possible to find lipid droplets that can represent
a metabolic defect or an energy reserve.
components of the cytoskeleton.
NEUROFIBRILS branch out throughout the cytoplasm of the soma and also extend into extensions.
At the ME it is possible to distinguish:
-MICROTUBULES
-NEUROFILAMENTS
-MICROFILAMENTS (actin): are associated with the plasma membrane
DENDRITE. They represent the SENSORY TERMINALS (afferents) of the neuron and transmit the signal towards the soma. Most neurons
have multiple dendrites, each of which arises from the cell body. Dendrites contain many mitochondria.
The branching and formation of numerous synaptic endings allows the neuron to receive and integrate a multiplicity of impulses.
On their surface there are SPINS that allow synapses to form with other neurons. These spines decrease with aging and poor nutrition.
Cytoplasmic prolongations can be distinguished on the basis of the direction of nerve impulse conduction.
AXON. It originates from the emergence cone of the cell body as a single prolongation extending a much longer distance than a dendrite. In
motor neurons, the axon can be 1 m long. The thickness is proportional to the conduction speed. While the dendrites can be numerous, the
axon can be only ONE, but it can branch producing collaterals, while when it terminates it gives rise to numerous AXON TERMINALS.
The EMERGENCY CONE, a pyramid-shaped region, is generally located opposite the
dendrites.
The INITIAL SEGMENT is represented by the portion between its point of emergence and
the first segment of myelin.
The axolemma of the initial segment presents a thin electron-dense layer, this area, rich in
microtubules and microfilaments, called the TRIGGERING AREA is the region where the
inhibitory and excitatory impulses are added to determine whether or not a
action potential.
The nervous impulse ORIGINS in the CONE OF EMERGENCY and in the INITIAL
STRETCH of the ABSOLEMMA.
The myelinated axons of the CNS and PNS are covered by neuroglial cells which deposit
the myelin sheath which gives it a whitish and translucent appearance, thus allowing the
WHITE substance to be distinguished from the GRAY substance in the CNS.
